RM: data analysis

What is ‘measure of central tendency’?

The measure of central tendency informs us about the middle value for a set of data

What are the different ways an average can be calculated?

Mean

Median

Mode

what is a pro of the mean?

It makes use of the values of all the data

What are the cons of the mean?

• The mean can be misrepresentative of the data as a whole if there are extreme values

• It cannot be used with nominal data

What is nominal data?

Nominal data is data that is categorised into named groups or labels, where the categories cannot be ordered or ranked. eg eye colour

what is the median?

The median is the middle value in an ordered list

What are the pros of the median?

• not effected by extreme scores

• Not as ‘sensitive’ as the mean because not all values are reflected in the median

What is the mode?

The mode is the value that is most common

What is the mode useful for?

The mode is useful when the data is in categories, eg nomina data

What is a con of the mode?

Not a useful way of describing data when there are several modes

What can be used to measure dispersion?

The range

Why can finding the range of a data set be useful?

It can be useful because it provides you with direct information: how varied or consistent the results are.

What are disadvantages of the range?

• It only uses the highest and lowest values, ignoring the rest of the data.

• It can be strongly affected by extreme values (outliers).

• It does not give detailed information about the overall spread of the data.

What is standard deviation?

Standard deviation is a measure of how much the values in a data set deviate (spread) from the mean.

What are the advantages of using standard deviation?

More precise measure of dispersion because all values are considered

What are the disadvantages of standard deviation?

difficult to calculate

Sensitive to outliers

what does the height of the bar in bar charts represent?

The frequency

What are bar charts most suitable for?

Data that is continuous such as nominal data (data set out in distinct categories)

What does the space between bars in bar chart represent?

The lack of continuity

What must the area within a bar in a histogram be proportional too?

The area of each bar must be proportional to the frequency of that category or class.

What must the horizontal axis be in a histogram?

The horizontal axis must represent the continuous, quantitative variable being measured, divided into equal or specified class intervals.

Why do the bars in histogram touch each other?

To show continuity

What does the y axis represent in a line graph?

Frequency

What must the values along the c axis be in a line graph?

Continuous

When is a scatter graph used?

When doing a correlational analysis

What is a normal distribution?

A normal distribution is a bell-shaped, symmetrical distribution where most values are clustered around the mean, and frequencies decrease evenly toward the extremes.

What is a positive skew?

A positive skew is where most of the distribution is concentrated towards the left of the graph

How are the mode, mean and median arranged in a positive skew?

Mode → median → mean

What is a negative skew?

A negative skew is where most of the distribution is concentrated towards the right of the graph

How are mode, mean and median arranged in a negative skew?

Mean → median → mode

Example of positive skew

Example of negative skew