Measures of Spread & Dispersion

Question 1

How do you calculate the lower quartile, Q1?

Answer 1

25 x 100 / the number of observations

• Use this number and go along to it on the sorted out line of numbers

Question 2

How do you calculate the upper quartile, Q3?

Answer 2

75 x 100 / the number of observations

• Use this number and go along to it on the sorted out line of numbers

Question 3

How do you calculate the inter quartile range?

Answer 3

Use the numbers that you went along to on the line and take them away from one another

Upper quartile - lower quartile

Question 4

How do you find the all 3 quartiles on a graph?

Answer 4

Plot at 25, 50 and 75, on the y axis go across until you hit the line, then go straight down

Question 5

How do you calculate the range?

Answer 5

Highest value take the lowest value

Question 6

What are some features of the range?

Answer 6

• Ignores the bulk of the data

- Only focuses on extreme values

Question 7

How do you calculate standard deviation for non-grouped data using a calculator?

Answer 7

1. Shift - Mode - Stat - Freq ON
2. Mode - Stat - 1-Var
3. Shift - 1 - Variable -SX

Question 8

How do you calculate standard deviation for grouped data using a calculator?

Answer 8

1. Find the midpoints and use this as X
2. Shift - Mode - Stat - Freq ON
3. Mode - Stat - 1-Var
4. Shift - 1 - Variable -SX

Question 9

What does a small variance mean?

Answer 9

The data set is huge

Question 10

What does a large variance mean?

Answer 10

The data set is small