Question

You have a list of 600 random, normally distributed numbers with a mean of 10 and a standard deviation of 2. Which of these statements is true?

About 489 numbers would lie between the values 8 and 12.,

About 408 numbers would lie between the values 6 and 10.,

About 285 numbers would lie between the values 10 and 14.,

Exactly 408 numbers would lie between the values 10 and 14., or

Exactly 285 numbers would lie between the values 8 and 12.

Answer 1

i think its A but its been such a long time since i did this stuff

Answer 2

ok thanks!

Answer 3

OK - what do oyu kow about the Normal curve?

have you heard of the 68, 95, 97.5 rule or similar?

Answer 4

Yes

Answer 5

so - the range 8 - 12 include how many standard deviations?

Answer 6

2?

Answer 7

wait

Answer 8

if i remember correctly it would be 68% in this range 8 - 12

Answer 9

which is 408

so its not A

Answer 10

so B?

Answer 11

OK - you are well on th eway here - keep going

Answer 12

B is not correct - because the range has changed

Answer 13

oh ok..

Answer 14

yea B is 6 -10

Answer 15

oh so it's D then?

Answer 16

hmm not sure

Answer 17

@MrNood said the range changed??

Answer 18

i'd have to look it up

my figure would give 408 between values 8 - 12 but thats not one of the options

Answer 19

You already worked out 408 in 8-12
So it cannot be 408 in 6-10

@welshfella Please do not give complete answers - Let OP understand this process

Answer 20

8 and 12 is in the range of 1 standard deviation about the mean 10

Answer 21

yea OK

Answer 22

I suggest you work out the population at each of these points , and then see which answers are correct