Question

The next two questions (18 and 19) refer to the following:

The heights of elementary school students are known to follow a normal distribution with mean 121 cm and standard deviation 5 cm.

Question 18 (1 point)

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What is the 60^th percentile of heights of elementary school students?

Question 18 options:

	122.68 cm
	124.00 cm
	124.63 cm
	122.25 cm
	125.21 cm

Question 19 (1 point)

Saved

A random sample of eight elementary school students is selected. What is the probability that their average height is between 122 cm and 123 cm?

Question 19 options:

	0.2214
	0.5483
	0.1819
	0.1551
	0.2051

Answer 1

  

mean = = 121

standard deviation = = 5

Question 18

Using standard normal table ,

P(Z < z) = 60%

P(Z < 0.25) = 0.6

z = 0.25

Using z-score formula,

x = z * +

x = 0.25 * 5 + 121 = 122.25

60th percentile = 122.25 cm

Question 19

= / n = 5 / 8 = 1.7678

= P[(122 - 121) / 1.7678< ( - ) / < (123 - 121) / 1.7678)]

= P(0.57 < Z < 1.13)

= P(Z < 1.13) - P(Z < 0.57)

= 0.8708 - 0.7157

= 0.1551

Probability = 0.1551