Question

I'm not sure if I am able to do these in excel, but if so what are the functions for them?

1. (2 pts) The weights of 8-week-old French Bulldog puppies follow a normal distribution. What percent of puppies weigh more than 2.35 standard deviations below the mean?

2. (4 pts) If a Chevy Trailblazer lasts for an average of 170,000 miles and a standard deviation of 25,000 miles, assuming mileage follows a normal distribution, what is the probability that the Trailblazer will last at least 180,000 miles?

Answer 1

The normal distribution is based on z-score. And we can do it directly into excel either by using z-score or by using given values directly.

a) Here z-score is -2.35 because it says '2.35 sd below the mean' and we need to find area to the right of it because it says 'more than'

Since we have z-value given directly here so we can use 'normsdist(z)' formula into excel. It gives area to the left of the z-value.

Here we need to find area of the right of z-value so we will use '=1-normsdist(-2.35)' into excel to get.

So, the answer is 0.9906

b) In this we have mean, standard deviation and x-value given so here instead of normsdist we will use norm.dist

This also gives area to the left of x-value whereas we need to find area to the right of given x-value. So, we will use '=1-NORM.DIST(180000,170000,25000,TRUE)' into excel to get the answer.

Excel output:

Answer for this is 0.3446 (rounded to 4 decimal places)

That's how we can use excel in such question.

I hope this will help. Thank you.