Qualitative and Quantitative Data, Levels of Measurement, Normal Distribution

What is qualitative data?

Information that describes qualities, characteristics and subjective experiences rather then being expressed numerically

Collected through interviews, observations, case studies

What is quantitative data?

Information that can be counted, measured and expressed numerically

Collected through experiments, surveys and observations

What are the different levels of measurements?

• Nominal

• Ordinal

• Interval

• Ratio

(NOIR)

What is meant by nominal data?

• Data that groups variables into categories/labels

• Type of qualitative data

• Lowest/Simplest level of measurement

• Examples= gender, eye colour

What is meant by ordinal data?

• Data that is presented in rank order however the difference between values is not necessarily equal

• Type of qualitative data

• Examples= survey responses from ‘strongly disagree’ to ‘strongly agree’

What is meant by interval data?

• The difference between each value is consistent and meaningful but there is no true zero point

• Type of quantitative data

• Examples= temperature, pH measure

What is meant by ratio data?

• The distance between each value is meaningful and there is a true zero point

• Type of quantitative data

• Examples= weight, height or age

When is the median the best measure of central tendency?

When the data set is skewed or its ordinal data

What is the mean the best measure of central tendency?

When the data is continuous and symmetrical (normally distributed)

When is the mode the best measure of central tendency?

When its nominal data

What is the most appropriate measure of central tendency when the data has outliers?

median

value of the mean can be distorted by outliers

In a normally distributed data set, which is greatest: mode, median or mean?

mode, median and mean are equal

Which measures of central tendency have only one value?

median and mean