# Thread: Statistics normal distribution question

1. ## Statistics normal distribution question

It has been found that to much TV increases a childs waist size

When the child is between 29 and 53 months, for each hour of tv watched per week, wasit circumference increases by mean 0.43mm. This increase forms a normal distribution with a standard devition of 0.11mm.

a) What is the probability that the waist size of one child increases less than 0.441mm/hour of tv in this time period?

b) Consider a group of 4 people. What is the probability that the mean waist size increase of this group is less than 0.4mm/hour of tv in this time period?

So the mean is 0.43, Sigma(sd) is 0.11, and x is 0.441. (i Think so)

I need to find the z-score so - z= x-(mean)/sigma

: the z score is 0.441-0.43/0.11
z= 0.1

The area for 0.1 is = 0.5398 (sorry i made an error- focus on part 2)

However, this answer is wrong so what did i do that was wrong?

For part two, Do I use the new X value to find the z - score , then the ara, then multiply that area by 4?

2. ## Re: Statistics normal distribution question

What is the answer? If you use that and the standard normal table, can you work backward to solve this?

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