T4: Measures Of Variability

Question 1

What is the measure of central tendency?

Answer 1

Summarises a dataset with a single value that is representative of the dataset

Question 2

What are the roles of measures of variability?

Answer 2

Inferential statistics and descriptive statistics

Question 3

What are inferential statistics?

Answer 3

Amount of variability effects the kind of statements we can make about our population

Question 4

What are descriptive statistics?

Answer 4

Variability is an interesting dataset in itself

Question 5

What are the three numerical measures of variability?

Answer 5

The range, variance, standard deviation

Question 6

What is the mean deviation and how do you calculate it?

Answer 6

The difference of any score from the mean and always sum to 0

Question 7

How do you calculate the mean and mean deviation?

Answer 7

All scores % amount of scores and to calculate the mean deviation it is score % mean

Question 8

What is the variance?

Answer 8

Sum of squared deviations from the mean divided by the # of scores

Question 9

How do you get variance (squared) to its original unit of measurement?

Answer 9

Take the square root of the variance by doing the standard deviation (S)

Question 10

How to calculate the standard deviation?

Answer 10

The average distance of the scores in a date set from their mean

Question 11

What is the inflection point?

Answer 11

Where the curve bends outwards and it is always 1 SD from the mean

Question 12

How do we determine a persons relative rank in the distribution?

Answer 12

Know their individual score, mean of the sample and standard deviation

Question 13

What does the Z score tell us?

Answer 13

How far away a score is from the mean and it allows us to interpret score in terms of relative standing, variability, by comparing with the standard normal curve

Question 14

What is the standard normal curve described by?

Answer 14

Units of standard deviation

Question 15

How can we determine what proportion of scores are less or more than the individual score?

Answer 15

Calculate the Z score
Draw a picture
Look up value of z on z-table to find the relative individual value

Question 16

For a z-distribution if we convert to z-value it will always have these same properties…

Answer 16

It is normal
individual score = 0
s = -1

Question 17

What are z scores used (as descriptives) to do?

Answer 17

Find the relative position of a data element in its distribution
Allow comparisons between scores from different distributions

Question 18

What do we compare across different distributions?

Answer 18

Interpret the score in terms of

relative standing and variability