Hypothesis Testing (Binomial Distribution) (Edexcel A Level Maths: Statistics): Exam Questions

Supplier claims that when it supplies bags of sugar, the proportion of bags that are damp is less than 8%.

The manufacturer takes a random sample of 70 bags of sugar from supplier and finds that only 2 of the bags are damp.

Carry out a suitable test to assess supplier ’s claim.

You should state your hypotheses clearly and use a 10% level of significance.

A machine fills packets with sweets and of the packets also contain a prize.

The packets of sweets are placed in boxes before being delivered to shops.

There are 40 packets of sweets in each box.

The random variable represents the number of packets of sweets that contain a prize in each box.

State a condition needed for to be modelled by

Kamil claims that the proportion of packets containing a prize is less than .

A random sample of 110 packets is taken and 9 packets contain a prize.

Use a suitable test to assess Kamil’s claim.

You should

• state your hypotheses clearly

• use a 5% level of significance

Harry is using the random variable  to test the hypotheses:

Harry states that the critical regions are  and 

Calculate the probability of incorrectly rejecting the null hypothesis.

Sally is using the random variable  to test the hypotheses:

Sally observes the value  for her test statistic.

(i) Calculate the p-value of the observed test statistic .

(ii) State, with a reason, the conclusion of Sally’s test if a 5% level of significance is used.

Charlie, the owner of a chocolate shop, claims that more than 60% of people can tell the difference between two brands of chocolate.  Charlie takes a random sample of 150 customers and asks them to taste both brands of chocolate.  He records that 103 of them could successfully tell the difference between the two brands of chocolate.

State suitable null and alternative hypotheses to test Charlie’s claim.   

Test, at the 10% level of significance, whether Charlie’s claim is justified.

The existing treatment for a disease is known to be effective in 73% of cases.  Dr Sabir develops a new treatment which she claims is more effective than the existing one.  To test her claim she uses the new treatment on a sample of 60 patients with the disease and uses a binomial distribution to model the number of them who are cured.

Explain two assumptions that Dr Sabir has made when using a binomial distribution to model the number of patients in the sample cured by the vaccine.

Dr Sabir notes that her treatment was effective for 51 out of the 60 patients used in the sample.

Test, at the 1% level of significance, the validity of Dr Sabir’s claim that her treatment is more effective than the existing one. State your hypotheses clearly.

State whether the conclusion would be different if a 5% level of significance had been used for this test instead of 1%. Give a reason for your answer.

A “double yolker” is an egg which contains two yolks.  It is stated that the probability of a chicken laying a double yolker is 0.1%.  A chicken farmer, Paolo, claims that double yolkers are rarer than the stated 0.1%.  To test his claim, Paolo records that his chickens lay 1217 eggs in a month and he uses these as his sample.  He discovers that none of these eggs are double yolkers.

Test, at the 5% level of significance, whether there is evidence to support Paolo’s claim that double yolkers are rarer than 0.1%. State your hypotheses clearly.

Paolo decides to take a larger sample so extends his test to three months.  During this time, a sample of 3425 eggs is formed and none of them are double yolkers.

Show that there is evidence, at the 5% level of significance, to support Paolo’s claim that double yolkers are rarer than 0.1%.

It is known that 61% of male dragons eat more than 20 sheep within a day.  Bill, a dragon breeder, suspects that the proportion of female dragons that eat more than 20 sheep within a day is different to males.

State suitable null and alternative hypotheses for a two-tailed test for Bill’s suspicion.

To test his suspicion, Bill observes a random sample of 80 female dragons during a full day and counts how many sheep they each eat.  He finds that 40 out of the 80 female dragons ate more than 20 sheep within the day.

Test, at the 5% level, whether there is evidence to support Bill’s suspicion.

State whether the outcome of the test would have been different, at the 5% level, if Bill had used a one-tailed test to check whether the proportion of females eating more than 20 sheep within a day is lower than the proportion of males. Give a reason for your answer.

Past information shows that 25% of adults in a large population have a particular allergy.

Rylan believes that the proportion that has the allergy differs from 25%.

He takes a random sample of 50 adults from the population.

Rylan carries out a test of the null hypothesis using a 5% level of significance.

Write down the alternative hypothesis for Rylan’s test.

Find the critical region for this test.

You should state the probability associated with each tail, which should be as close to 2.5% as possible.

State the actual probability of incorrectly rejecting for this test.

Rylan finds that 10 of the adults in his sample have the allergy.

State the conclusion of Rylan’s hypothesis test.

A dentist knows from past records that 10% of customers arrive late for their appointment.

A new manager believes that there has been a change in the proportion of customers who arrive late for their appointment.

A random sample of 50 of the dentist's customers is taken.

Write down

• a null hypothesis corresponding to no change in the proportion of customers who arrive late

• an alternative hypothesis corresponding to the manager's belief

Using a 5% level of significance, find the critical region for a two-tailed test of the null hypothesis in (a).

You should state the probability of rejection in each tail, which should be less than 0.025

Find the actual level of significance of the test based on your critical region from part (b).

The manager observes that 15 of the 50 customers arrived late for their appointment.

With reference to part (b), comment on the manager’s belief.

Historical records show that England wins 45% of Ashes test cricket games.  Rory believes that the probability of England winning a game has decreased due to a new manager.  To test this, he looks at their results in the next 17 games and identifies the number of times that England wins, denoted .

Using a 5% level of significance, identify the critical region to enable Rory to test his claim. State the hypotheses clearly.

England have wins five series in the next 17 games. Use your answer in part (a) to state, with a reason, whether this sample supports Rory’s claim.

State an assumption you made when using a binomial distribution to model the scenario.

It is known that there is a 0.35% chance of picking up a virus when downloading a file from a particular website.  After a security update, a security analyst believes that the chances of picking up a virus have been reduced.  The analyst wishes to use a hypothesis test with a 5% level of significance to test her belief.

In a sample of 1542 files downloaded from the website, 1 virus is detected. 

Find the conclusion of the analyst's test. State the hypotheses clearly.

At a school it is known that 80% of students achieve 3 or more A* to C grades in their A levels.  The principal claims that another local school has a different proportion of A* to C grades at A level.

Last year the other school had 57 out of 80 students achieve 3 or more A* to C grades at A level.

Using a two-tailed hypothesis test, test the principal’s claim at the 5% significance level stating suitable null and alternative hypotheses.

On a particular Pokémon game, it is possible to create offspring through breeding.  Sometimes when two Pokémon are bred together, their offspring possess a hidden ability.

One Pokémon fan website, , claims that the probability of producing offspring with a hidden ability is 0.6.  Another website,, claims the probability is higher.

Maya conducts an experiment and finds that 38 out of 50 of her Pokémon’s offspring possess a hidden ability.

Use Maya’s sample to test the claim of website   against website  at the 5% significance level, stating your null and alternative hypotheses clearly.

Website  claims that the probability of producing offspring with a hidden ability is different to 0.7.

Using a two-tailed hypothesis test with the same sample, test the claim at the 5% significance level.

A single observation is taken from a discrete random variable to test the hypotheses

where   is a positive integer.

The probability of rejection for each tail of the critical region is as large as possible and at most 5%.

Given that one tail of the critical region is , find the value of .

Find the other tail of the critical region for the test.

Find the probability of incorrect rejecting the null hypothesis.

It is known that customers have an 83% success rate when attempting to order bundles of 5 or more festival tickets from a particular website.  A second website claims that its customers have a greater probability of success.

State suitable null and alternative hypotheses to test the second website’s claim.

In one day, 1159 out of 1358 bundles of 5 or more tickets are successfully ordered from the second website.

Test the second website’s claim using a 1% significance level.

It is suggested that instead of using a 1% significance level for the test, the critical region could have been used for testing the second website’s claim against observed data for the number of successes out of 1358 attempted orders. 

Find the probability of incorrectly rejecting the null hypothesis if that critical region is used.

Nguyen is using the large data set to investigate claims by a local newspaper that the chance of rain on a given day in Leuchars is 18%. She believes that this is incorrect.

Nguyen finds that out of the 184 days in 1987 for which she has data, 43 were rainy.

(i) Using a 5% level of significance, test the newspaper’s claim.  State your null and alternative hypotheses clearly.

(ii) With reference to the large data set, state one limitation to your conclusion about the newspaper’s claim.

Nguyen also finds that in 2015 there were 37 rainy days out of the 184 for which she has data.

State, giving a reason for your answer and without calculating any additional probabilities, whether the chances of rejecting the newspaper’s claim are higher or lower with this sample.

Nguyen chooses to combine the data from the two years and test at the 5% significance level.  Nguyen believes that the chance of rain is higher than 18%. 

Calculate the p-value for this test and comment on Nguyen’s belief.

A nursery has a sack containing a large number of coloured beads of which 14% are coloured red.

Aliya takes a random sample of 18 beads from the sack to make a bracelet.

State a suitable binomial distribution to model the number of red beads in Aliya’s bracelet.

After several children have used beads from the sack, the nursery teacher decides to test whether or not the proportion of red beads in the sack has changed.

She takes a random sample of 75 beads and finds 4 red beads.

Stating your hypotheses clearly, use a 5% significance level to carry out a suitable test for the teacher.

Find the p‐value in this case.

Nationally it is reported that four out of five people can write with their right hand.  Edward, an education researcher, takes a random sample of 30 children under the age of 18 years old and records the number of them, , who can write with their right hand.

If the national proportion applies to the sample, write down a suitable distribution for . State any assumptions that you make.

Edward believes that the proportion of children who can write with their right hand differs from the national proportion for all people.  To test his belief, he uses his sample of 30 children.

State suitable null and alternative hypotheses to test Edward’s belief.

Using a 10% level of significance, find the critical region for a two-tailed test for Edwards’ belief. You should state the probability of rejection for each tail, which should be less than 0.05 for each.

Find the actual level of significance of a test based on your critical values.

Out of the 30 children in the sample, Edward recorded that 20 of them write with their right hand.

Comment on Edward’s belief based on this observation.

A single observation, , is taken from a discrete random variable to test  against    

The critical regions are chosen as being   and .

Calculate the probability of incorrectly rejecting the null hypothesis when conducting this test.

The probability of a wild Asian elephant living past 40 years old is 45%. 

Rosie, a zoologist, obtains data on 25 elephants in captivity and records their ages at death. She suspects that the proportion of Asian elephants that live past 40 years old is smaller for those in captivity than those in the wild.

Using a 1% level of significance, find the critical value of a one-tailed hypothesis test to enable Rosie to test her suspicion. Clearly state your hypotheses.

Rosie finds that only one elephant, out of the 25 in captivity, lived past 40 years old. 

(i) Write down the conclusion of the hypothesis test based on this information.

(ii) Calculate the actual probability that this observed result has led to the incorrect conclusion.

A newspaper article claims that 60% of animal species have become extinct since 1970.  Iggy, a taxonomic biologist, has been studying animal extinction statistics and believes that the proportion is different to the newspaper’s claim.

Iggy collects a random sample of 500 species that were recorded as being in existence in 1970 and records the number that are now extinct.  He uses multiple sources to verify the species’ taxonomic status and finds that the number of extinct species could be as low as 319 or as high as 329.

Iggy wants to use his findings to test his belief, but he also wants to make sure that the test will support his belief for all possible values of the number of extinct species. What is the smallest possible integer percentage value he could use for a significance level to make sure that the test supports his belief?

Iggy repeats this process with a different random sample of 1000 species for which the taxonomic status is more certain, and in this second sample he finds the total number of extinct species to be 650.

Show that the evidence from this second sample offers better support for Iggy’s hypothesis than the evidence from his first sample.

Historic company data shows that the proportion of customers ordering a large vegetable box from Lakebridge Organics is 0.4.

Last week a random sample of 35 customers’ orders was taken and it was found that 21 of them had ordered a large vegetable box.

Test, at the 5% significance level, whether this suggests that the proportion of customers ordering large vegetable boxes has increased. State your hypotheses clearly.

Historic company data shows that the proportion of customers ordering a medium vegetable box is also 0.4.  Lucinda, a delivery driver, suspects that the proportion of current customers ordering medium boxes is different from 0.4.  She takes a random sample of 40 customers’ orders.

(i) Stating your hypotheses clearly, identify the critical regions for a hypothesis test at the 5% significance level.

(ii) State the actual level of significance of the test.

(iii) Of the 40 orders, 21 of them were for medium vegetable boxes. State whether this supports Lucinda’s suspicion at the 5% level of significance.

A football team, Dinamo Galacticos, are trying to decide on a colour for their new kit.  They are told by a local sports commentator that the proportion of games won by teams wearing red is 0.5.

The manager takes a random sample of 20 games where one team wears red and finds that  of them are won by the team in red.  Assuming that the proportion of games won by teams in red really is 0.5, then the probability that n or fewer games out of 20 would be won is equal to 0.1316 correct to 4 decimal places.

Find the value of .

The manager decides to increase her random sample to include 50 games.  She suspects that the actual proportion of games won by teams in red is lower than 0.5.

(i) Using a 5% level of significance, find the critical region for a one-tailed hypothesis test. State your hypotheses clearly.

(ii) Using a 10% level of significance, find the largest number of games that could be won by teams wearing red without the test suggesting that the manager’s suspicions are unfounded.

The sports commentator later says that he may have gotten mixed up, and that he thinks it is actually teams wearing green that win 50% of their games.

Given that teams wearing green have won 12 games from the last 35 in which they played, test at the 5% significance level whether the commentator’s new claim is justified. You must clearly state your null and alternative hypotheses.

A catering company’s past records show that the proportion of their customers who are vegetarian has previously been 0.2.  The company decides to take a random sample of 30 current customers to test whether that figure 0.2 is still valid for their current customer base.

Let  denote the number of vegetarians in the sample. Find the critical region for a two-tailed test using a 10% significance level, stating the actual probability in each tail.

The number of vegetarian customers in the sample is 11.  One of the company’s employees used the same sample to suggest that this shows that the proportion of vegetarian customers has not just changed but has in fact increased.

Use this test statistic to test, at the 5% level of significance, whether the proportion of vegetarian customers has increased. State your hypotheses clearly.

A random variable has distribution  .

In order to test the hypotheses

a random observation of  is taken and found to be 5.

Carry out a hypothesis test at the 10% significance level.

Another random variable has distribution  .

A random observation of is taken and found to be 1. Using the same hypotheses as above, find the maximum value of  for which  would not be rejected at the 10% significance level.

Another random observation of  is taken and found to be .  For the same hypotheses as above, this provides evidence to reject  at the 5% significance level. 

Using your answer to part (b) as the value for , find the possible values of .