Question

- Suppose we know that examination scores have a population standard deviation of σ = 25. A random sample of n = 400 students is taken and the average examination score in that sample is 75. Find a 95% and 99% confidence interval estimate of the population mean µ.

Answer #1

Suppose we have the following paired observations of variables
X and Y:
X Y
18 40
14 30
20 20
22 20
19 10
27 0
Calculate the values of the sample
covariance and sample correlation between X and Y. Using this
information, how would you characterize the relationship between X
and Y?
(12 points)
Suppose X follows a normal distribution with mean µ = 50 and
standard deviation σ = 5.
(10 points)
What is the...

Suppose scores exams in statistics with an unknown population
mean and a sample standard deviation of 2 points. A random sample
of 16 scores is taken and gives a sample mean. (sample mean score)
of 8. Find the confidence interval estimate for the population mean
test score ( the mean score of all tests).
Find a 90% confidence interval for the true (population) mean of
statistics test scores.

Suppose we are interested about a confidence interval for the
population mean scores on an exam. A random sample of 38 scores is
taken and gives a sample mean (sample mean score) of 118. What is
the 95% Error Bound (EBM) if the population standard deviation is 8
points?

Suppose a college math scores are approximately normally
distributed with mean μ=70 and standard deviation σ=10.
a. What score should a student aim to receive to be in the 95th
percentile of the math scores?
b. You took a random sample of 25 students from this population.
What is the probability that the average score in the sample will
be equal to or greater than 75?

Suppose the population standard deviation, σ, is 30 based upon
previous studies. We would like to estimate the population mean
within ±10 of its true value, at a significance level of .05 (95%
Confidence interval). What sample size should be taken?

The scores of a certain population on the Wechsler Intelligence
Scale for Children (WISC) are thought to be Normally distributed
with mean μ and standard deviation σ = 10. A simple random sample
of 25 children from this population is taken and each is given the
WISC. The mean of the 25 scores is = 104.32. Suppose a histogram of
the 25 WISC scores is the following. Based on this histogram, we
would conclude that a 95% confidence interval of...

A random sample is drawn from a population having σ = 15.
a. If the sample size is n = 30 and the sample mean x = 100,
what is the 95% confidence interval estimate of the population mean
µ?
b. If the sample size is n = 120 and the sample mean x = 100,
what is the 95% confidence interval estimate of the population mean
µ?
c. If the sample size is n = 480 and the sample...

7. If I have a population of an unknown mean and unknown
standard deviation, what is the 95% confidence interval estimate of
the mean if a. A random sample of size 25 gives a mean of 50 and a
standard deviation of 12 b. A random sample of size 16 gives a mean
of 50 and a standard deviation of 12
8. The average cost per night of a hotel room in New York City
is $325. Assume this estimate...

Suppose that scores on Statistics of government and public
School in UMAC are normally distributed. To estimate the average
score on the for all students, I take my class as a random sample
of size 25. The sample yielded mean, = 35 and sample standard
deviation, s = 15. Give a 95% confidence interval for the average
score on the of Statistics for all government and public School
students.

Question #8: The score of the LSAT examination have a population
mean µ = 70 and population standard deviation σ = 10. Answer the
questions below and show work.
1.) A random sample of 64 individuals is taken. What is the
probability that the sample mean is below 71?
2.) A random sample of 100 individuals is taken. What is the
probability that the sample mean is below 71?

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