Measures of central tendency & dispersion

Question 1

What are descriptive statistics?

Answer 1

• use of summary statistics to identify trends & analyse sets of data

Question 2

What are measures of central tendency?

Answer 2

• the general term for any measure of the average value in a set of date
• mode, median, mean

Question 3

What is the mean and how is it calculated?

Answer 3

• arithmetic average calculated by adding up all values then dividing by total number of values

Question 4

What is a strength and limitation of using the mean?

Answer 4

strengths
- most sensitive of the measures as it includes all the values in data set within the calculation
limitation
- mean is easily distorted by extreme values which may not represent the data set overall

Question 5

What is the median and how is it calculated?

Answer 5

• the middle value in a data set when scores are arranged from lowest to highest

Question 6

What are the strengths and limitations of using the median?

Answer 6

strengths
- not affected by extreme scores
- easy to calculate
limitation
- less sensitive (actual values of lower & higher numbers are ignored)

Question 7

What is the mode?

Answer 7

• the most frequent value in a data set

Question 8

What are the strengths and limitations of using the mode?

Answer 8

strengths
- sometimes the only method of measure u can use (data in categories)
- easy to calculate
limitations
- not useful if there are many different modes
- not representative of the whole data set

Question 9

What is meant by measure of dispersion?

Answer 9

• the general term for any measure of the spread or variation in a set of scores
• range, standard deviation

Question 10

What is the range and how is it calculated?

Answer 10

• calculation of the spread of scores and is worked out by subtracting the lowest value from the highest value and adding 1 (accounts for margin error)

Question 11

What are the strengths and limitations of using the range?

Answer 11

strength
- easy to calculate
limitations
- only takes into account the most extreme values >unrepresentative of the data set as a whole
- range is influenced by outliers (distorted by extreme values)
- does not indicate whether most numbers are closely grouped around the mean or spread out

Question 12

What is standard deviation?

Answer 12

• more sophisticated measure of the spread of set of scores
• tells us how far scores deviate from the mean

Question 13

What are the strengths and limitations of using standard deviation?

Answer 13

strengths
- much more precise measure of dispersion as it includes all the values within final calculation
limitation
- can be distorted by a single extreme value > not representative

Question 14

What does a low standard deviation suggests?

Answer 14

• reflects the fact that the data is tightly clustered around the mean
• may imply that all participants responded in a fairly similar way

Question 15

What does a high standard deviation suggest?

Answer 15

• the spread of scores is much greater
• not all participants were affected by the IV in the same way
• may be a few anomalous results