1. True or False. Justify for full credit.
(a) The normal distribution curve is always symmetric to 0.
(d) In a hypothesis testing, if the p-value is less than the significance
level α, we do not have sufficient evidence to reject the null hypothesis.
Hints
Quiz #5
1. True or False. Justify for full credit.
(a) The normal distribution curve is always symmetric to 0. Hint: Where is the
mean?
(b) If the variance from a data set is zero, then all the observations in this data
set are identical. Hint: What does variance mean?
(c) P(AOR A complement) =1, where A complement is the complement of A.
Hint: What does complement mean?
(d) 1d – If the p-value is less than or equal to the chosen significance level (α),
the test suggests that the observed data are inconsistent with the null hypothesis,
so the null hypothesis must be rejected. However, that does not prove that the
tested hypothesis is true.
(e) The volume of milk in a jug of milk is 128 oz. The value 128 is from a discrete
data set. http://statistics.wikidot.com/ch6
The IQ scores are normally distributed with a mean of 100 and a standard
deviation of 15.
100 + or – sd (15) =
1 sd =?
2 sds = ? 3sds =
?
2.. What is the probability that a randomly selected person has an IQ between 85
and 115?
3. Find the 90th percentile of the IQ distribution. Hint: 15 times 1.3???
4. If a random sample of 100 people is selected, what is the standard deviation
of the sample mean?
standard deviation = sd/sqrt of n
5. A random sample of 100 light bulbs has a mean lifetime of 3000 hours.
Assume that the population standard deviation of the lifetime is 500 hours.
Construct a 95% confidence interval estimate of the mean lifetime. Show all
work. Just the answer, without supporting work, will receive no credit
xbar – 1.96 SD/SQRT(100) < mean < xbar +1.96 SD/SQRT(100)
where xbar = sample mean
xbar = 3000 hours, SD = 500 hours, n = 100