Data analysis: Descriptive statistics

Question 1

What are measures of central tendency?

Answer 1

• the general term for any measure of the average value in a set of data
• e.g. mean, median and mode

Question 2

What is the mean?

Answer 2

• arithmetic average calculated by adding up all the values and dividing by the no. of values there are
• more representative of the data as a whole
• easily distorted by extreme values

Question 3

What is the median?

Answer 3

• the central value in a set of data when values are arranged from lowest to highest
• extreme scores don’t affect it
• easy to calculate
• less sensitive since not all scores are included in the final calculation

Question 4

What is the mode?

Answer 4

• the most frequent occurring value in a set of data
• easy to calculate
• only method you can use for data in categories

Question 5

What are measures of dispersion?

Answer 5

• the general term for any measure of the spread or variation in a set of scores
• e.g. range & standard deviation

Question 6

What is the range?

Answer 6

• calculation of the dispersion in a set of scores worked out by subtracting the lowest from the highest score and adding 1 as a mathematical correction

Question 7

What is standard deviation?

Answer 7

• a sophisticated measure of dispersion in a set of scores
• tells us how much scores deviate from the mean by calculating the difference between the mean and each score
• all the differences are added up and divided by the number and score which gives variance
• SD is the square root of the variance
• the larger the SD the greater the spread within a set of data so not all pps were affected by the IV in the same way and there may be a few anomalous results
• low SD means the data is tightly clustered around the mean which implies that all pps responded in a similar way
• SD can be distorted by a single extreme value