Data Handling: Computation & Descriptive Statistics (AQA GCSE Psychology): Flashcards
Exam code: 8182
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In the number 20.059, what do the 5 and the 9 refer to?
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In the number 20.059, what do the 5 and the 9 refer to?
The 5 refers to 5 hundredths, and the 9 refers to 9 thousandths.
Define standard form.
Standard form is a way of dealing with very large or very small numbers without calculations becoming too cumbersome.
Write 835,000,000,000 in standard form.
8.35 × 10¹¹. The 835 is reduced to a number between 1 and 10, then ‘to the power of’ is added to express the size of the number.
True or False?
Small numbers written in standard form use a positive index.
False.
The index must be negative — 0.000000000000761 is written as 7.61 × 10⁻¹³.
How do you reduce a fraction to its simplest form?
Find the highest common factor between the numerator and the denominator, and divide both by it — so 20/50 = 2/5.
How do you change a fraction into a decimal?
Divide the numerator by the denominator — so 2/5 = 2 ÷ 5 = 0.4.
What do ratios allow researchers to do?
Compare quantities as proportions of the whole data set. Like fractions, they should be reduced to their simplest form — so 5:25 = 1:5.
In AQA GCSE Psychology, which type of ratio are students most commonly asked to calculate?
A part-to-part ratio — usually comparing two groups or conditions directly, such as Group A compared to Group B.
When writing a ratio, what determines the order of the numbers?
The order given in the question — this must always be followed, as it determines the order in which the ratio is written.
Define a percentage.
A percentage is a number or quantity calculated as a proportion out of 100.
Express 65% as a decimal and as a fraction.
As a decimal, 0.65; as a fraction, 13/20.
How do you calculate a percentage from a data set?
Multiply the numerator by 100, then divide by the denominator — 63 out of 70 is 63 × 100 = 6300 ÷ 70 = 90%.
Jenny surveys 60 students and 18 prefer Crunchy Nut Cornflakes. Calculate the percentage.
30% — calculated as 18 × 100 = 1800 ÷ 60 = 30%.
Round 596,321 to one significant figure.
600,000.
Decimal places are rounded from just after the decimal point; significant figures are rounded from the first digit.
Decimal places are rounded from just after the decimal point; significant figures are rounded from the first non-zero digit.
Round 0.00038967 to two significant figures.
0.00039.
How could you estimate the result of 619 × 280?
By rounding the numbers up or down before carrying out the calculation — 600 × 300.
Define the mean.
The mean calculates the average score of a data set: the total of all values divided by the number of values.
Calculate the mean of 4, 6, 7, 9.
4 + 6 + 7 + 9 = 26; 26 ÷ 4 = 6.5.
Give one advantage of the mean.
It is the most sensitive measure of central tendency, as it takes all scores into account — so it is more likely to provide a representative result.
Give one disadvantage of the mean.
It is sensitive to extreme scores (outliers), so can only be used when scores are reasonably close. The mean may also not appear in the data set itself.
Define the median.
The median is the middle value of a data set — the positional average.
What must you do before finding the median?
Arrange the data into numerical order, with the lowest score at the beginning.
How do you find the median with an odd number of values?
There is a single middle value — for 20, 43, 56, 78, 92, 67, 48 (7 scores), ordered: 20, 43, 48, 56, 67, 78, 92. The middle (4th) value is 56, so the median = 56.
How do you find the median with an even number of values?
Take the halfway point between the two middle values — add them together and divide by 2. For 8, 8, 9, 9, 9, 10, 12, 13, 15, 16 (10 scores), the two middle values are 9 and 10: (9 + 10) ÷ 2 = 9.5.
Give one advantage of the median.
It is not affected by extreme scores and is easy to calculate.
Give one disadvantage of the median.
It does not use the value of every score, so it is not representative of the whole data set. It is also impractical on large data sets, as sorting into order becomes time-consuming as the set grows.
Define the mode.
The mode is the most frequently occurring score in a data set — mode means most often.
Calculate the mode of 3, 3, 3, 4, 4, 5, 6, 6, 6, 6, 7, 8.
Count how often each score appears: 6 appears most often (four times), so the mode = 6.
When is the mode used?
When the researcher cannot use the mean or the median — for example with categorical (nominal) data, such as favourite colour, where scores have no numerical order.
A data set which includes two modes is described as .
A data set which includes two modes is described as bimodal.
Give one advantage of the mode.
It is less likely to be affected by extreme scores, and is useful for qualitative data where frequencies of theme are analysed.
Give one disadvantage of the mode.
It does not use the value of every score, so it is not representative of the whole data set — and bimodal or multimodal data blurs the meaning.
Define the range.
The range is a measure of dispersion: the difference between the lowest and highest scores in a data set.
Give one advantage of the range.
It provides a quick, broad overview of the data, and is easy to calculate.
Calculate the range of 4, 4, 6, 7, 9, 9.
9 − 4 = 5. The range is 5.
True or False?
The range tells you about all the scores in a data set.
False.
It only takes into account the two most extreme scores, so a single unusually high or low score can distort it, making it unrepresentative of the data set as a whole — and it gives no information about the scores in between.
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