Question

There is a 90% probability that a Normally distributed random variable be less than:

1) 0.90 standard deviations above its mean

2)1.28 standard deviations above its mean  

3) 1.50 standard deviations above its mean

4)1.64 standard deviations above its mean

5)2.33 standard deviations above its mean

Answer 1

Solution:

There is a 90% probability that a normally distributed random variable be less than:

Answer: 2) 1.28 standard deviations above its mean  

Explanation:

We know that the z-score tells us how many standard deviations above or below a particular value is from the mean.

So here we have to find here

We can find the value of using the standard normal table. We have to find the z-value corresponding to area = 0.90.

Using the standard normal table, we have:

We can also use the excel function to find the value of . The excel function is: