80+ Two different Lage groups were surveyed about
the amount of time they spent on social media.
The results are shown in the two frequency
polygons below. The same time intervals were
used for both graphs.
11-year old students
15-year old students a) How many 15-year old
80
students took part in
70
70
the survey?
(1)
60
60
50
50
b) How many more 15-year
640
240
old students than 11-year
30
30
old students spent
20
20
between 35 and 45 mins
on social media?
0
0
0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80
(1)
Time (mins)
Time (mins)
Total marks: 2
Frequency
Frequency
10
10

(co 3) the times that customers spend in a book store are normally distributed with a mean of 39.5 minutes and a standard deviation of 9.4 minutes. a random sample of 25 customers has a mean of 36.1 minutes or less. would this outcome be considered unusual, so that the store should reconsider its displays? no, the probability of this outcome at 0.035, would be considered usual, so there is no problem yes, the probability of this outcome at 0.035, would be considered unusual, so the display should be redone no the probability of this outcome at 0.359 would be considered usual, so there is no problem yes, the probability of this outcome at 0.965 would be considered unusual, so the display should be redone