Maths question (1 Viewer)

[A.void.that.thinks]

Hi, I just need some help with this question. The answer is B and I understand why the mean would decrease but don’t quite understand how they worked out that the standard deviation would decrease.
Any help would be amazing!

 

[hiiitsme]

72 is 5/7 standard deviations above the mean whereas 60 is -1 standard deviation below the mean

Standard deviation is a measure of spread about the mean

a minus one means more 'weight' has been placed below the mean therefore the standard deviation decreases

I think this is right

 

[hellohowslife]

lol the way I do it is just test it with the numbers 60,67,74 and then with added 60,72 to see what happens