Ch2

What is interpolation

What is interpolation

The process of estimating medians, quartiles, and percentiles in a grouped frequency table. Assuming the data values are equally distributed within each class.

Q1

• n/4th data value

• Lower quartile

Q2

• n/2th data value

• Median value

Q3

• 3n/4th data value

• Upper quartile

Interquartile range

Q3 - Q1

Interpolation formula

(x - x1)/(x2 - x1) = (y - y1)/(y2 - y1)

What is a measure of location?

A single value which describes a position in a data set.

What is a measure on central tendency?

a single value which describes the central position in a data set.

When is it best to measure mode?

When data is qualitative or quantitative with either a single mode or bimodal. Not very informative if each value only occurs once.

When is it best to measure median?

Used for quantitative data, best for extreme values because they do not affect it.

When is it best to measure mean?

Used for quantitative data and uses all pieces of data, therefore gives a true measure of data. It is affected by extreme values.

Calculate mean for data in a frequency table?

sum of products of data values and their frequencies/sum of the frequencies

What is qualitative data?

Data that is written in words, descriptive or interpreted with language.

What is quantitative data?

Data that is written in numbers, countable and measurable.

What is discrete data?

Numerical data that can only take certain values e.g. shoe size

What is continuous data?

Numerical data that can take any value within a given range e.g. heights of some adults

What are examples of measures of location

• mean, median, mode

• quartiles

• percentiles

What are examples of measures of spread

• range

• interquartile range

• interpercentile range

• variance and standard deviation