Question

22. An index that is a standardized measure used in observing infants over time is approximately normal with a mean of 96 and a standard deviation of 10.  What index score is less than 33​% of the population index scores?

	a.	91.60
	b.	0.3707
	c.	0.44
	d.	100.40
	e.	52.24

Answer 1

Using standard normal table,

P(Z < z) = 33%

= P(Z < z) = 0.33  

z = -0.44 ( Using standard normal z table,)

Using z-score formula  

x= z * +

x= -0.44 *10+96

x= 91.6