Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed.

Compute a 90% CI for the true average porosity of a certain seam if the average porosity for 50 specimens from the seam was 4.85 with a sample standard deviation of .65.

A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained if he wishes the estimate to be within

4

percentage points with

95​%

confidence if​(a) he uses a previous estimate of

26%?

​(b) he does not use any prior​ estimates?

​(a)

nequals=nothing

​(Round up to the nearest​ integer.)​(b)

nequals=nothing

​(Round up to the nearest​ integer.)

The true percentage of left-handed people is 13% (p = .13)

1. a. If we survey two hundred people, how many left handers do you expect to survey?

b. If you repeat this survey, will you always get this number of left-handers (the expectation)? Why or why not?

c. What is the spread (standard deviation) of the sample proportions?

d. Use the empirical rule to describe where we expect sample proportions to lie if we repeated this survey (with size of 200 people) over and over again

68% of sample proportions would lie between ______________and _____________

95% of sample proportions would lie between _____________and______________

99.7% of sample proportions would lie between _____________and______________

The following data represent the 50 companies' percentage of revenues spent on research and development:

13.5 8.4   10.5   9.0 9.2   9.7   6.6   10.6   10.1   7.1

8.0   7.9   6.8   9.5   8.1 13.5   9.9   6.9    7.5    11.1

8.2   8.0   7.7 7.4   6.5 9.5   8.2 6.9   7.2   8.2

9.6   7.2   8.8 11.3   8.5 9.4   10.5   6.9   6.5    7.5

7.1   13.2   7.7   5.9   5.2 5.6   11.7   6.0   7.8    6.5

Construct a stem-and-leaf display.

In the NBA LeBron James had a free throw success percentage of 68.9% for the 2016-17 season. If during a game, LeBron shot 6 free throws, find the probability that he

a) Made exactly 4 free throws

b) Made at least 3 free throws

c)If over the course of a season LeBron shoots 600 free throws, find the mean and standard deviation of the probability distribution for the number of free throws he makes. Mean: Standard Deviation:

d) Use the range rule of thumb to determine what range would you expect the number of successful free throws over the season.

You believe a higher percentage of students receive “passed advanced” in your school as opposed to a neighboring school. A random sample of 84 students from your school showed that 19 were pass advanced, and a random sample of 156 students from a neighboring school showed that 31 were pass advanced. If appropriate, test your hypothesis at the significance level .05.

A: Are the assumptions met?

B: State the hypotheses

C:What is the test statistic?

D: What is the p-value?

E:What is your conclusion?

A) Test at 5% level individually if the mean percentage for each of the means is different from 10%.

B) Obtain a 95% confidence interval for the difference of means for the two countries.

C) Test an appropriate pair of hypotheses for the two means at 5% level of significance

21.

What percentage of water on earth's surface is readily available to terrestrial life?

Group of answer choices

97.5%

71%

5%

1%

less than 0.01%

22.

Dams can be detrimental to all of the following *EXCEPT*

Group of answer choices

fishermen

aquatic wildlife

rural and ur

Based on the use of water in an average home in the United States, which of the following methods would conserve the most water?

Group of answer choices

Decreasing the water temperature when taking a shower

Replacing old toilets with new low flow toilets

Turning the water off while brushing teeth

Drinking more bottled water instead of water from the tap

Taking baths instead of 5 minute showers

24.

Which of the following actions are people concerned about water pollution most likely to do?

Group of answer choices

Dispose of used car oil in the storm drain

Switch from organic to inorganic fertilizers

Pull weeds by hand rather than applying herbicides

Switch to a laundry detergent with high phosphate content

25.

Which of the following is NOT a water pollutant that threatens human health?

Group of answer choices

Cholera

Ozone

Mercury

E. coli

Arsenic

ban electricity customers

towns and farms upstream of the dam location

23.

Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.76.

(a) Compute a 95% CI for the true average porosity of a certain seam if the average porosity for 24 specimens from the seam was 4.85. (Round your answers to two decimal places.)

.............................. ,...................................

(b) Compute a 98% CI for true average porosity of another seam based on 10 specimens with a sample average porosity of 4.56. (Round your answers to two decimal places.)

......................................... , ...............................

(c) How large a sample size is necessary if the width of the 95% interval is to be 0.44? (Round your answer up to the nearest whole number............ specimens

(d) What sample size is necessary to estimate true average porosity to within 0.23 with 99% confidence? (Round your answer up to the nearest whole number.)...........
specimens