Intro, terms + definitions

Question 1

Population

Answer 1

The entire set of items from which you draw data for a statistical study

Question 2

Sample

Answer 2

A selected group of data taken from a population.
There are many types of samples and it is important to choose a relevant sample
according to the data you are collecting

Question 3

Random

Answer 3

Happening without method or conscious decision

Question 4

Tally

Answer 4

A means of collecting data using five bar gate tally marks

Question 5

Discrete data

Answer 5

Quantitative Data that takes set values.
For example : shoe size, number of pets owned, marks in a times table test

Question 6

Continuous data

Answer 6

Quantitative data that can take any value.
For example : height, time taken to complete a race, temperature

Question 7

Raw data

Answer 7

Data that is in the form in which it was collected so is not sorted.

Question 8

Ranked data

Answer 8

Quantitative Data that is put in order from smallest to largest or vice versa

Question 9

Grouped data

Answer 9

Data that is sorted into different classes

Question 10

Mode

Answer 10

This is a form of average.
It is the data value that occurs the most often

Question 11

Modal group

Answer 11

The class or group of data that contains the most data so has the highest frequency

Question 12

Median

Answer 12

This is a form of average.
The middle piece of data when the data is ranked.
The position of the median is calculated using (𝑛+1)/2
where 𝑛 is the number of pieces of data.
For example, if you have 67 pieces of data, (67+1)/2
= 34 so the median is the 34th piece of data when it is ranked.

Question 13

Mean

Answer 13

This is a form of average that is represented by 𝑥̅(𝑥 bar).
To calculate the mean, you divide the sum of all the data by the number of pieces of data
This formula is written as
𝑥̅= (∑ 𝑥)/𝑛
If your data is given in a frequency table then the formula becomes
𝑥̅= (∑ 𝑥f)/∑f

Question 14

Range

Answer 14

Highest value – lowest value
This is a very crude measure of spread because it includes any possible outliers

Question 15

Mid-range

Answer 15

The is the value that lies midway between the lowest and highest value.
It is an easy average to find when the distribution of your data is symmetrical
Mid-range =
(ℎ𝑖𝑔ℎ𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒+𝑙𝑜𝑤𝑒𝑠𝑡 𝑣𝑎𝑙𝑢𝑒)/2

Question 16

Inter-quartile range

Answer 16

This is a measure of spread that eliminates any possible outliers by using the middle 50%
of data
IQR = Upper Quartile – Lower Quartile = Q3 – Q1
The lower quartile is the median of the first half of ranked data
The upper quartile is the median of the second half of ranked data
If n is odd then the first and second halves are the sets of data before and after the
median

Question 17

Semi-interquartile
range

Answer 17

Half the Interquartile range

Question 18

Standard deviation

Answer 18

A measure of spread that uses the distances of each piece of data from the mean

Question 19

Variance

Answer 19

Variance = the square of the standard deviation

Question 20

Outlier

Answer 20

A piece of data that does not fit in with the general distribution of the whole data set
A possible outlier lies more than 2 standard deviations from the mean
or further than 1.5 x IQR below the LQ or above the UQ

Question 21

Distribution

Answer 21

The way in which data is spread, shown by an outline of the shape of a diagram
Key words:
Unimodal, bimodal, symmetrical, uniform, negative skew, positive skew

Question 22

Stem and Leaf Diagram

Answer 22

You put the data into categories of sorts (the first digit/s of thier numbers). The first digits will be on one side of the line, and then all the following digits separated by commas will follow.
63, 67, 72
6|3, 7
7|2