Question

Suppose that scores on an exam are normally distributed with a mean of 80 and variance of 81. What is the first quartile?

A.) 97.6

B.) 63.3

C.) 86.1

D.) 73.9

E.) 87.1

Answer #1

Solution:-

Given that,

mean = = 80

standard deviation = = `81=9

Using standard normal table,

The z dist'n First quartile is,

P(Z < z) = 25%

= P(Z < z) = 0.25

= P(Z < -0.6745 ) = 0.25

z = -0.6745

Using z-score formula,

x = z * +

x = -0.6745 * 9+80

x = 73.9

correct anser is D

Suppose the scores on a statistic exam are normally distributed
with a mean of 77 and a variance of 25.
A. What is the 25th percentile of the scores?
B. What is the percentile of someone who got a score of 62?
C. What proportion of the scores are between 80 and 90?
D. Suppose you select 35 tests at random, what is the proportion
of scores above 85?

The scores of students on an exam are normally distributed with
a mean of 250 and a standard deviation of 40. (a) What is the first
quartile score for this exam? (Recall that the first quartile is
the value in a data set with 25% of the observations being lower.)
Answer: (b) What is the third quartile score for this exam?
Answer:

A set of exam scores is normally distributed with a mean = 80
and standard deviation = 10.
Use the Empirical Rule to complete the following
sentences.
68% of the scores are between _____ and ______.
95% of the scores are between ______ and _______.
99.7% of the scores are between _______ and ________.
Get help: Video

Suppose the scores of students on an exam are Normally
distributed with a mean of 303 and a standard deviation of 39. Then
approximately 99.7% of the exam scores lie between the numbers and
such that the mean is halfway between these two integers. (You are
not to use Rcmdr for this question.)

Suppose exam scores are normally distributed with a mean of 70
and a standard deviation of 6. The probability that someone scores
between a 70 and a 90 is?

Student scores on the Stats final exam are normally distributed
with a mean of 75 and a standard deviation of 6.5
Find the probability of the following:
(use 4 decimal places)
a.) The probability that one student chosen at random scores above
an 80.
b.) The probability that 10 students chosen at random have a mean
score above an 80.
c.) The probability that one student chosen at random scores
between a 70 and an 80.
d.) The probability that...

Suppose scores on a college entrance exam are normally
distributed with a mean of 550 and a standard deviation of 100.
Find the score that marks the cut-off for the top 16% of
the scores. Round to two decimal places.

Suppose scores on a college entrance exam are normally
distributed with a mean of 550 and a standard deviation of 100.
Find the score that marks the cut-off for the top 16% of the
scores. Round to two decimal places.

Suppose your score on an exam is 76 and the exam scores are
normally distributed with a mean of 70. Which is better for you: A
distribution with a small standard deviation or a large standard
deviation? Explain.

Exam scores in a MATH 1030 class is approximately normally
distributed with mean 87 and standard deviation 5.2. Round answers
to the nearest tenth of a percent.
a) What percentage of scores will be less than 93? %
b) What percentage of scores will be more than 80? %
c) What percentage of scores will be between 79 and 88? %

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 13 minutes ago

asked 19 minutes ago

asked 29 minutes ago

asked 36 minutes ago

asked 41 minutes ago

asked 57 minutes ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 1 hour ago

asked 2 hours ago