Question

Scores on a national math test are Normally distributed, with a mean score of 490 and a standard deviation of 50. Which test score represents the top 20%, rounded to the nearest whole number?
Find the z-table here.

426
448
532
554

Answer 1

Answer:

532

Step-by-step explanation:

The score that represents the top 20% = A score = 80%

Z score for 80% percentile = 0.842

We solve using the z score formula

z = (x-μ)/σ, where

x is the raw score = ??

μ is the population mean = 490

and σ is the population standard deviation = 50

Hence:

0.842 = x - 490/50

Cross Multiply

0.842 × 50 = x - 490

x = 0.842 × 50 + 490

x = 42.1 + 490

x = 532.1

Approximately = 532

Therefore, the test score = 532

Answer 2

Answer:

532

Step-by-step explanation:

edg 2020-2021