Question

Scores of adults aged 60 to 64 on a common IQ test are approximately Normally distributed with mean 90 and standard deviation 15

1. Since IQ scores of adults aged 60 to 64 are Normally distributed with mean 90 and sd 15, then about 40% of the scores are between

a. 60 and 120

b. 45 and 135

c. 85 and 90

d. the 25th and 75th percentile

e. the 30th and 70th percentile

2. What range of IQ scores contains th ecentral 95% of the population of adults aged 60 to 64?

a. 75 to 105

b. 60 to 120

c. 30 to 150

d. 45 to 135

3. The third quartile of the distribution of IQ scores of adults aged 60 to 64 is between

a. 90 to 105

b. 90 to 75

c. 105 to 120

d. 60 to 75

4. Suppose we call an IQ of 90 "normal" for adults aged 60 to 64. What percent of the population have "below normal" IQs?

a. about 50%

b. less than 50%

c. More than 50%

d. Cant tell from the information given.

Answer #1

Q 1 ) X ~N(90, 15)

The 40% of score lies between 30th and 70th percentile . It also lies between 25th and 75th percentile but the minimum range is 30th and 70th percentile

Answer: Option e) the 30th and 70th percentile

Q 2) Range of IQ scores contains 95% Confidence is

Solution : The critical value of Z for 95% CI is +/-2 (using empirical rule )

Therefore the lower bound is

The upper bound is

Answer: Option b. 60 to 120

Q 3) The Z value for third quartile is 0.674

Therefore the third quartile is

Hence it is lie between 90 to 105

Answer: Option a) 90 to 105

Q 4) Answer: a. about 50%

Because IQ scores follows normal distribution and the mean score is 90. the area below the mean is 50%

Assume that adults have IQ scores that
are normally distributed with a mean of 100 and a standard
deviation of 15. Find the probability that a randomly selected
adult has an IQ between 115 and 130.
(a)
.6700 (b)
.1359 (c)
.9082 (d)
.1596 (e) .1628
5 Refer to question 4
above. Find the IQ score at Q1 or the 25th percentile.
This is the score which separates the bottom 25% from the top
75%.
(a)
89.95 (b)...

Assume that adults have IQ scores that are normally distributed
with a mean 105 and standard deviation of 20. a. Find the
probability that a randomly selected adult has an IQ less than 120.
b. Find P90 , which is the IQ score separating the bottom 90% from
the top 10%. show work

A) Assume that adults have IQ scores that are normally
distributed with a mean of 100 and a standard deviation of 15. Find
the probability that a randomly selected adult has an IQ between 90
and 120. (Provide graphing calculator sequence)
B) Assume that adults have IQ scores that are normally
distributed with a mean of 100 and a standard of 15. Find P3D,
which is the IQ score separating the bottom 30% from the top 70%.
(Provide graphing calculator...

adults have IQ scores that are normally distributed with a mean of
100 and a standard deviation of 15
a. what IQ score respresents the 95th percentile?
b. what IQ score represents the 50th percentile?
show how you got the answer step by step, clearly just trying
to check my work thanks !

Adults have a IQ scores that are normally distributed with a
mean of a 100 and a standard deviation of 15.
a) what percentage of scores are less than 103?
b) what percentage of scores are between 60 and 130?
c) what is the IQ score seperating the bottom 25% from the
rest?
thank you.

For question 10, assume that adults have IQ scores that are
normally distributed with a mean of 100 and a standard deviation of
15. Find the probability that a randomly selected adult has an IQ
of the following: 10. Find the area under the standard normal curve
for the following: • Less than 115. • Greater than 131.5 • Between
90 and 110 • Between 110 and 120

Assume that adults have IQ scores that are normally distributed
with a mean of mu equals 105?=105 and a standard deviation sigma
equals 20?=20. Find the probability that a randomly selected adult
has an IQ between 92 and 118.

Assume that adults have IQ scores that are normally distributed,
with a mean of 107 and a standard deviation of 15. Find the
probability that a randomly selected individual has an IQ between
75 and 117.

Assume that adults have IQ scores that are normally distributed
with a mean of mu equals 105 and a standard deviation sigma equals
20. Find the probability that a randomly selected adult has an IQ
between 91 and 119.

6. Assume that adults have IQ scores that are normally
distributed with mean 100 and standard deviation 15. In each case,
draw the graph (optional), then find the probability of the given
scores. ROUND YOUR ANSWERS TO 4 DECIMAL PLACES
a. Find the probability of selecting a subject whose score is
less than 115. __________
b. Find the probability of selecting a subject whose score is
greater than 131.5. __________
c. Find the probability of selecting a subject whose score...

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