**The normal distribution curve is always symmetric to 0.**

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

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