Question

A certain mental development index for infants is a standardized measure used in observing infants over time. It is approximately normal with a mean of 99 and a standard deviation of 19. Find the​ z-score corresponding to the upper quartile (Q3) of a normal distribution.

Answer 1

Answer:

0.67449

Step-by-step explanation:

Let $Q_3$ be the  3rd quartile of normal distribution  .

-z-score corresponding to the upper quartile can be calculated in excel as:

• In Excel, click on any empty cell'
• Type  the function NORMINV
• Enter the probability as 0.75, mean= 0 and standard deviation=1
• Click the enter button.

-The output is 0.67449. Hence, the​ z-score corresponding to the upper quartile (Q3) of a normal distribution is 0.67499