Descriptive Statistics

Question 1

What are the measures of central tendency?

Answer 1

Mean

Median

Mode

Question 2

What is the mean?

Answer 2

Arithmetic average

Add up and divide by n

Question 3

What are the strengths of the mean?

Answer 3

Most sensitive

Takes all scores into account

Question 4

What are the weaknesses of the mean?

Answer 4

Affected by extreme values (outliers) which can skew data

Question 5

What is the median?

Answer 5

Middle value in an ordered list

Question 6

What are the strengths of the median?

Answer 6

Not affected by extreme values

Question 7

What are the weaknesses of the median?

Answer 7

Not as sensitive as the mean

Difficult to calculate with a large data set

Question 8

What is the mode?

Answer 8

Most frequently occurring value in a data set

Question 9

What are the strengths of the mode?

Answer 9

Useful for nominal data

Simplest to calculate

Question 10

What are the weaknesses of the mode?

Answer 10

Not useful when there are many modes

Question 11

What are the measures of dispersion?

Answer 11

Range

Standard deviation

Question 12

What is the range?

Answer 12

Subtract lowest from highest number

Question 13

What are the strengths of the range?

Answer 13

Convenient

Easy to calculate

Question 14

What are the weaknesses of the range?

Answer 14

Affected by extreme values (outliers)

Doesn’t reflect distribution

Question 15

What is standard deviation?

Answer 15

Mean distance of values from the mean

Question 16

What are the strengths of standard deviation?

Answer 16

Most precise, uses all the values

Question 17

What are the weaknesses of standard deviation?

Answer 17

May hide extreme values

Not immediately sensed

Question 18

What does a high and low standard deviation show?

Answer 18

High SD - the spread is wide

Low SD - scores are clustered

Question 19

What are bar charts?

Answer 19

Show the relative size of the data collected

Bars shouldn’t touch because the data isn’t continuous

Question 20

What are frequency tables?

Answer 20

Focus on groups of scores

e.g. how often each event occurred

Frequency is calculated by totalling the number of tallies for each group

Question 21

What are histograms?

Answer 21

Groups of numbers into ranges

Used to represent the data in a frequency table

Bars should be touching because the data is continuous

Frequency axis must start at 0

Question 22

What are scatter diagrams?

Answer 22

Represents the strength and direction of a relationship between co-variables in a correlational analysis

Correlational data, dot for x and y values

Positive correlation, scatter from bottom left to top right

Negative correlation, scatter from top left to bottom right

Question 23

What is normal distribution?

Answer 23

Normal distribution is a bell-shaped symmetrical frequency curve showing a mean, median and mode which all fall at the mid-point

Question 24

What is skewed distribution?

Answer 24

Skewed distribution occurs when the mean, median and mode are not similar, and if scores are bi-modal (or multi-modal)

Negative skew - the scores in a distribution are bunched towards the right. The mode is to the right of the mean because the mean is dragged to the left by extreme scores tailing in a negative direction (tail to the left)

Positive skew - the scores in a distribution are bunched towards the left. The mode is to the left of them mean because the mean is dragged to the right by extreme scores tailing a positive direction (tail to the right)