Collecting and Analysing Data

Question 1

For a sample to be reliable, how much of the population must it be of?

Answer 1

At least 10%

Question 2

What is primary data?

Answer 2

Data I collect myself

Question 3

What is secondary data?

Answer 3

Data collected by somebody else

Question 4

What is a frequency diagram?

Answer 4

A bar chart

Question 5

What is a modal class?

Answer 5

The class with the highest frequency

Question 6

What is a stem and leaf diagram?

Answer 6

Question 7

How do you draw a frequency polygon?

Answer 7

Plot the midpoints against the frequency and join the points with straight lines (freqency on the y axis)

Question 8

How do you find the mean from a class based frequency table?

Answer 8

Add a midpoint of class column

Add a midpoint x frequency column

Estimated mean is midpoint x frequency divided by the sum of the frequencies

Question 9

How do you estimate the range from a frequency table?

Answer 9

Uppermost value subtract the lowermost value

Question 10

What is the lower quartile?

Answer 10

Where the bottom 25% of the data is

Question 11

How do you calculate the lower quartile?

Answer 11

By finding the value 1 quarter of the way up the list

(Sum of items in list + 1) x 0.25

Question 12

What is the upper quartile?

Answer 12

Shows where the top 75% of the data is

Question 13

How do you calculate the upper quartile?

Answer 13

By finding the value 3/4 of the way up the list

Median + Lower Quartile = Upper Quartileth item

Number of items in the list x 0.75th item

Question 14

Label this box plot

Answer 14

Question 15

What is the cumulative frequency?

Answer 15

The sum of consecutive frequencies

Question 16

How do you draw a cumulative frequency graph?

Answer 16

Add a cumulative frequency column

In the first row write the frequency of the first group

In the second row, write the frequency of the combined first and second groups

In the third row, write the frequency of the combined first, second and third groups

Plot the upper bound of each class interval on the x axis

Plot the cumulative frequency on the y axis

Question 17

What is a histogram?

Answer 17

Similar to a bar chart, a histogram is a diagram where the area of the bar gives the frequency, rather than the height. The vertical axis is the frequency density.

Question 18

How do you calculate frequency density?.

Answer 18

Frequency

Class Width

(Frequency/ Class Width)

Question 19

How do you draw a histogram?

Answer 19

Add a class width column

Add a frequency density column

Plot the class on the x axis

Plot the frequency density on the y axis