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Research Methods

Descriptive statistics, tables and graphs

  • 3 things to know
  • Components 01 and 02

Overview

The mode, median, mean and range, percentages, ratios, fractions, standard form, significant figures and estimation, the normal distribution, frequency tables, bar charts, histograms and line graphs.

What you need to know

Answer each one before you reveal it.

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Key term

Eight participants recalled 12, 7, 15, 9, 11, 14, 8 and 10 words. What is the median?

Numbers

Six participants scored 14, 18, 11, 16, 20 and 17 on a memory test. Calculate the mean score.

Key term

Five participants recalled 6, 7, 8, 9 and 30 words. Why is the median a better average than the mean for these scores?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Ten participants rated their mood from 1 to 7 and gave these ratings: 3, 5, 5, 6, 2, 5, 4, 6, 3, 5. What is the mode?

    Model answer

    The mode is 5. The rating of 5 occurs four times, more often than any other rating.

  2. 2

    Reaction times were grouped as follows: 200 to 249 milliseconds, 4 people; 250 to 299 milliseconds, 11 people; 300 to 349 milliseconds, 7 people; 350 to 399 milliseconds, 3 people. What is the modal class?

    Model answer

    The modal class is 250 to 299 milliseconds. The class holds 11 people, the highest frequency in the table.

  3. 3

    Eight participants recalled 12, 7, 15, 9, 11, 14, 8 and 10 words. What is the median?

    Model answer

    The median is 10.5 words. The middle two scores in order are 10 and 11, and halfway between them is 10.5.

  4. 4

    Six participants scored 14, 18, 11, 16, 20 and 17 on a memory test. Calculate the mean score.

    Model answer

    The mean score is 16. The scores add up to 96, and 96 ÷ 6 = 16.

  5. 5

    Five participants recalled 6, 7, 8, 9 and 30 words. Why is the median a better average than the mean for these scores?

    Model answer

    The mean is 12, pulled upwards by the extreme score of 30. The median of 8 is unaffected by the extreme score, so it is more typical.

  6. 6

    In one condition, participants scored 4, 9, 13, 7 and 18. Calculate the range, and give one weakness of the range.

    Model answer

    The range is 14, because 18 − 4 = 14. A weakness is that the range uses only the two most extreme scores.

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