Measures of central tendency and dispersion

Question 1

Define descriptive statistics.

Answer 1

The use of graphs, tables and summary statistics to identify trends and analyse sets of data.

Question 2

What does it mean to measure central tendency?

Answer 2

The general term for any measure of the average value in a set of data.

Question 3

How do you calculate the mean?

Answer 3

Add up all of the scores or values in a data set and divide them by the total number of scores that there are.

Question 4

Strength of the mean?

Answer 4

Most sensitive of the measures of central tendency as it includes all of the scores/values in a data set. More representative of the data as a whole.

Question 5

Limitation of the mean

Answer 5

Extreme values can easily distort the results so it does not represent the data overall.

Question 6

What is the median?

Answer 6

The middle value in a data set.

Question 7

How do you work out the median?

Answer 7

List the scores in the data set from lowest to highest and find the middle. In an odd number of scores, the median is easily identified whereas in an even number the median is halfway between the two middle scores.

Question 8

Strength of the median

Answer 8

Extreme scores do not affect it. Easy to calculate.

Question 9

Limitation of the median

Answer 9

Less sensitive than the mean and extreme values may be important. The actual values of lower and higher numbers are ignored.

Question 10

What is the mode?

Answer 10

The most frequently occurring score/value within a data set.

Question 11

What is it called if in a data set there are two modes?

Answer 11

bi-modal

Question 12

How to find the mode?

Answer 12

Find the most common number in a data set.

Question 13

Strength of using the mode.

Answer 13

Easy to calculate.

Question 14

Limitation of using the mode.

Answer 14

When there are several modes in a data set, this information is not very useful.

Question 15

Give some measures of central tendency.

Answer 15

Mean
Median
Mode

Question 16

What does it mean to measure dispersion?

Answer 16

Measuring the spread or variation in a set of scores.

Question 17

Give some examples of measures of dispersion.

Answer 17

Range
Standard Deviation

Question 18

How do we calculate the range?

Answer 18

A simple calculation of the spread of scores by taking the lowest value from the highest value. Usually you would add one after.

Question 19

Why would we add 1 after calculating the range?

Answer 19

Allows for the fact that raw scores are often rounded up (or down) when they are recorded. (Accounts for a margin of error).

Question 20

Give a strength of using the range.

Answer 20

Easy to calculate.

Question 21

Give a limitation of using the range.

Answer 21

Only takes into account the two extreme values and this may be not be representative of the whole data set.
Does not indicate whether most numbers are closely grouped around the mean or spread out- standard deviation does show this.

Question 22

What is standard deviation?

Answer 22

A sophisticated measure of dispersion in a set of scores. It tells us by how much, on average, each score deviates from the mean.

Question 23

What does a high standard deviation mean?

Answer 23

Not all participants are affected by the IV in the same way because data is widely spread.

Question 24

What does a low standard deviation mean?

Answer 24

Data is tightly clustered around the mean which may imply that all participants responded in a fairly similar way.

Question 25

Strength of standard deviation.

Answer 25

Much more precise measure of dispersion than the range as it includes all values in the final calculation.

Question 26

Limitation of standard deviation.

Answer 26

Can be distorted by a single extreme value.