Data: Descriptive Statistics

Question 1

What are the various measures of central tendency

Answer 1

• Mode
• Median
• Mean

Question 2

How do you decide which measure of central tendency to use

Answer 2

Based on the levels of measurement

Question 3

which measure of central tendency you’d use if the data was nominal

Answer 3

Mode

Question 4

which measure of central tendency you’d use if the data was ordinal

Answer 4

• the median
• then the mode if calculating the median isn’t possible

Question 5

which measure of central tendency you’d use if the data was interval/ratio

Answer 5

• preferably the mean
• however, if the data is skewed…
• you need to calculate the median
• then the mode if calculating the median isn’t possible

Question 6

What is the strength of using the mean

Answer 6

• takes all the scores into account so it is the most sensitive

Question 7

What is the weaknesses of using the mean

Answer 7

• impacted by extreme values (i.e. outliers) - it will be skewed (artificially inflated or deflated)
• not useful when a decimal point is not an option for the data (e.g. 2.4 cola bottles)

Question 8

What is the strength of using the mode

Answer 8

• Not impacted by extreme values (i.e. outliers) — it will not be skewed (artificially inflated or deflated)
• useful for nominal data as it is the only method

Question 9

What is the weakness of using the mode

Answer 9

• Doesn’t take all the scores into account so it is not as sensitive
• there may be several or none

Question 10

What is the strength of using the median

Answer 10

• not impacted by extreme values (i.e. outliers) - it will not be skewed (artificially inflated or deflated)

Question 11

What is the weaknesses of using the median

Answer 11

• Doesn’t take all the scores into account so it is not as sensitive

Question 12

EXAMPLE:
In an unethical experiment 3 groups of 8 lab rats were given a maze to complete and times were recorded in seconds.
Group 1) Rats given brain lesions - 35, 27, 26, 27, 28, 79, 27, 30
Group 2) Rats with tails cut off - 15, 10, 18, 22, 8, 49, 16, 22
Group 3) Rats with eyes damaged - 33, 33, 32, 28, 67, 45, 24, 29
Which measure of central tendency should be used + why?

Answer 12

• the data was ratio, however there were outliers in the groups
• therefore calculating the median is the most appropriate measure of central tendency
• because we can’t calculate the mean because there are outliers

Question 13

Describe the characteristics of a Bar chart

Answer 13

used for nominal (category/not continuous data):
- frequency = Y-axis
- categories = X-axis
- gaps between each bar represents the lack of continuity
For experiments: IV = X-axis, DV = Y-axis

Question 14

Describe the characteristics of a Histogram

Answer 14

Used for continuous data:
- frequency = Y-axis (it must start at 0)
- continuous data = X-axis
- no gap between each bar, represents continuity

Question 15

Describe the characteristics of a Line graph

Answer 15

• frequency = Y-axis (must start at 0)
• used for continuous data = displayed on X-axis
• each dot is connected by a line

Question 16

Describe the characteristics of a Pie chart

Answer 16

• suitable for nominal data
• each slice represents a portion of
• each slice is calculated by a portion of 360’

Question 17

Describe the characteristics of a Scatter diagram

Answer 17

• each covariable is plotted on y and x axis
• suitable for continuous data (displayed on both x and y axis)
• each dot represents 2 scores
• the scatter of the dots indicates the relationship between the covariable

Question 18

What is the definition of range

Answer 18

The distance between the top and bottom values in the data set

Question 19

How do you calculate the range in psychology

Answer 19

Subtract the lowest from the highest, then add one

Question 20

Why is it helpful to calculate the range

Answer 20

• useful to describe data
• help explain differences in data, not visible by only calculating the mean

Question 21

What does a high standard deviation score mean

Answer 21

Scores are spread widely from the mean

Question 22

What does a low standard deviation score mean

Answer 22

Scores are clustered near the mean

Question 23

What does it mean if the standard deviation score is 0

Answer 23

All the values in the data set are the same

Question 24

How do you calculate a standard deviation

Answer 24

Question 25

What is meant by standard deviation

Answer 25

A measure of dispersion, shows how the data is spread around the mean

Question 26

Explain the steps you would follow to calculate a standard deviation

Answer 26

1) calc the mean of the scores in the data set
2) take mean away from each score in data set
3) square each difference
4) add the sum of all the squared differences
5) divide this by the number of scores minus one
6) Calc the square root of the divided data ——> this is the standard deviation

Question 27

What is the strength of using a range

Answer 27

Easy to calculate

Question 28

What is the disadvantage of using a range

Answer 28

• impacted by extreme values (e.g. outliers), it will be skewed (artificially inflated or deflated)
• Fails to take into account the distribution of scores around the mean (don’t know if the scores are close together or far apart)

Question 29

What is the strength of using standard deviation

Answer 29

• more precise and informative measure of dispersion than range (because it takes all the values into account)
• Highlights if the mean is an appropriate measure of central tendency
• Used in further statistical analysis, such as computing skewness
• less affected by anomalous results than range scores

Question 30

What is the weakness of using standard deviation

Answer 30

• can only be used if the data set is normally distributed and not skewed
• more difficult to calculate than the range score
• can only be used when data collected is ordinal level or above
• Can only be used where an IV is plotted against frequency