Question

Hello everyone, can someone help with problem 2 on Quiz 2? When standard dev is 0 its obvious we are getting the mean every time, but with say std. dev 20, 95% of the values are within 3 std. dev. so thats (100 +- 60)*1000. But how do you come up with an expected value and why is it so much larger for std. dev. 40

Answer 1

Is this a program or just math?

Answer 2

it is a quiz problem so you have to read the code and come up with the expected value

Answer 3

you are not allowed to run the code so there has to be a mathematical reasoning for it

Answer 4

You aren't giving enough information either way.

Answer 5

import random
tots = [0.00]*3
maxVals = [0.0]*3
mean = 100.0
stdDevs = [0.0, 20.0, 40.0]
for i in range(1000):
for j in range(len(tots)):
next = random.gauss(mean, stdDevs[j])
tots[j] += next

what are the expected values of tots

Answer 6

Interesting... I would expect the expected values to be the mean, or 100.0 for each individual element... by definition.

Answer 7

thats what i thought, but the answer is [100,000 100,000 1000,000]

Answer 8

oh wait, I see.

Answer 9

The loop is adding 100 each time, but it does this 1000 times.

Answer 10

yea, i get the first two 100,000s, but how does standard deviation 40 result in the value 1000,000?

Answer 11

I don't think it should

Answer 12

me too