Descriptive statistics

Question 1

What are descriptive statistics?

Answer 1

a way of describing quantitative data and identifying any patterns or trends.

Question 2

What are the two methods for descriptive statistics?

Answer 2

Measures of central tendency
Measures of dispersion

Question 3

What are the levels of measurements?

Answer 3

nominal
ordinal
interval

Question 4

What is nominal data?

Answer 4

data that is presented in named groups or categories. For example, ice cream flavours or film genres.

Question 5

What is ordinal data?

Answer 5

data that is presented in rank order, but the distance between points on the scale is unknown eg. most to least, but the gap between each score would be different,

Question 6

What is interval data?

Answer 6

data that can measured in fixed units with equal distance between points on the scale. For example, temperature measured in centigrade, or weight measured in kilograms.

Question 7

What are measures of central tendency?

Answer 7

This informs us about central (or middle) values of a set of data. They are averages – ways of calculating a typical value for a set of data.
hese can be calculated in different ways, each one appropriate for a different situation - mean, median and mode.

Question 8

When is the mean used?

Answer 8

Used for interval data.

Question 9

Strength of using the mean?

Answer 9

Most sensitive measure of central tendency because it takes account of the exact distance between all of the values of all the data.

Question 10

Limitation of using the mean?

Answer 10

Due to sensitivity – can be distorted by extreme values therefore becoming unrepresentative of the data set

Question 11

When to use the median?

Answer 11

Interval and ordinal data

Question 12

Strength of using the median?

Answer 12

Not affected by extreme scores, can be easier to calculate than the mean and can be used for ordinal data

Question 13

Limitation of using the median?

Answer 13

Not as sensitive, the exact values are not reflected…just the middle numbers.

Question 14

When to use the mode?

Answer 14

nominal, ordinal and interval

Question 15

Strength of using the mode?

Answer 15

Unaffected by extreme values and is the only measure which can be used for nominal data.

Question 16

Limitation of using the mode?

Answer 16

It is not useful for explaining data when there is more than one mode

Question 17

What is the measures of dispersion?

Answer 17

This refers to how dispersed or spread out data items are.

Question 18

How to find out the measures of dispersion - range?

Answer 18

find the lowest value and highest value, minus the lowest value from the highest value then +1.

Question 19

Strength of measures of dispersion - range?

Answer 19

Easy to calculate

Question 20

Limitation of measures of dispersion - range?

Answer 20

Is affected by extreme values

Fails to take into account the distribution of values, therefore does not give a fair representation of the general spread of data

Question 21

How to find out the measures of dispersion - standard deviation?

Answer 21

a measure of the average distance between each data item above and below the mean.

Question 22

Strength of measures of dispersion - standard deviation?

Answer 22

much more sophisticated measure of dispersion because it takes into account all the exact values in a data set.

Question 23

Limitation of measures of dispersion - standard deviation?

Answer 23

Like the mean, SD can be distorted by extreme values.

Question 24

Data distributions?

Answer 24

When data is displayed on a graph, we often see a bell curve – the way this bell curve looks helps us to find out how the data is distributed.
We use the average and then the standard deviations to work out how the data is distributed.

Question 25

Normal distibution?

Answer 25

This is a classic bell shaped curve and shows the data is equally distributed. The distribution is symmetrical around the middle point

Question 26

Skewed distibutions?

Answer 26

Negatively skewed (left skewed) – the mean is lower than the mode and median.

Positively skewed (right skewed) - the mean is higher than the mode and median.