representing data

Question 1

what are the measures of central tendency

Answer 1

mean , median , mode

Question 2

how to calculate weighted mean

Answer 2

(sum of weighting factor x number)/sum of all weights

Question 3

What does a weighted mean take into account

Answer 3

relative sizes of each piece of data

Question 4

how to work out the mean from grouped data

Answer 4

1. find the mid point by
   (lowest value + highest value)/2
2. midpoint x frequency
3. midpoint x frequency/frequency

Question 5

What does the range show and how is it calculated

Answer 5

the difference between lowest and highest value in a data set

highest value - lowest value

Question 6

what does the interquartile range show

Answer 6

the extent to which the central 50% of values within the dataset are dispersed.

Question 7

interquartile range formula

Answer 7

subtracting the lower quartile from the upper quartile.

Question 8

What is the semi interquartile range

Answer 8

Half of the interquartile range

Question 9

What are the difference between bar charts and histograms

Answer 9

Bar charts are used to present categorical data (and have gaps between the bars) whereas histograms are used to present numerical, continuous data.

Question 10

How does a dot plot show data

Answer 10

dot plots use dots instead of bars that would be used in a bar chart to show where data ends.

Question 11

What does a cumulative frequency diagram show

Answer 11

creates a running total of the amounts within a table.

Question 12

How do you work out cumulative frequency

Answer 12

add frequencys together

Question 13

How do we draw cumulative frequency diagrams

Answer 13

plot the highest value from each range against the cumulative frequency, then jin them up

to identify the median, find the middle value

upper quartile = middle between median and highest value

lower quartile = middle between median and lowest value

Question 14

what does a box plot show

Answer 14

a visual representation of the median and quartiles of a set of data.

Question 15

If the centre of a box plot is to the left, what does this mean

Answer 15

positively skewed data

Question 16

If the centre of a box plot is to the right, what does this mean

Answer 16

negatively skewed data

Question 17

on a scatter diagram, what do we plot along the x and y axis

Answer 17

We plot the independent variable (the one we hypothesise is doing the ‘affecting’) along the x-axis.

We plot the dependent variable (the one we hypothesise is ‘being affected’) along the y-axis.