Question

(20 PTS!!)

The dot plot below shows the amount of time two random groups of students took to brush their teeth:

Based on visual inspection of the dot plots, which of the following groups, if any, shows a greater average time required to brush their teeth?

Group R
Group S
Both groups show about the same average time.
No conclusion about average time can be made from the data.

Answer 1

The correct option is C.

Explanation:

In a dot plot, the number of dots above a number represents the frequency of that number.

From the given dot plot it is clear that number of dots for group R is 21 and the time taken by the students of groups R are

45, 50, 50, 55, 60, 60, 70, 75, 80, 85, 90, 90, 95, 100, 100, 105, 110, 110, 115, 120, 120

The average of the data is

`Average=(\sum x)/(n)`

`Average=(45+50+50+55+60+60+70+75+80+85+90+90+95+100+100+105+110+110+115+120+120)/(21)`

`Average=(1785)/(21)`

`Average=85`

From the given dot plot it is clear that number of dots for group S is 17 and the time taken by the students of groups S are

50, 55, 60, 60, 65, 70, 70, 80, 90, 90, 95, 100, 105, 110, 110, 115, 120

`Average=(50+55+60+60+65+70+70+80+90+90+95+100+105+110+110+115+120)/(17)`

`Average=(1445)/(17)`

`Average=85`

The average time of both groups are same.

Since both groups show about the same average time, therefore the correct option is C.