In: Mechanical Engineering
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 2 percentage points with 90% confidence if
(a) he uses a previous estimate of 32%?
(b) he does not use any prior estimates?
(a) n=_____
(Round up to the nearest integer.)
(b) n=______
(Round up to the nearest integer.)
In: Statistics and Probability
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 3 percentage points with 99% confidence if (a) he uses a previous estimate of 38%? (b) he does not use any prior estimates?
In: Statistics and Probability
A political candidate has asked you to conduct a poll to determine what percentage of people support her. If the candidate only wants a 4% margin of error at a 90% confidence level, what sample size is needed?
In: Statistics and Probability
A political candidate has asked you to conduct a poll to determine what percentage of people support her. If the candidate only wants a 7% margin of error at a 90% confidence level, what size of sample is needed? ____
In: Statistics and Probability
It is difficult to determine a person’s body fat percentage accurately without immersing him or her in water. Researchers hoping to find ways to make a good estimate immersed 20 male subjects, then measured their waist shown in the table.
|
a) Treating waist as the explanatory variable, x, determine the estimates of ?1and ?0.
In: Statistics and Probability
College officials want to estimate the percentage of students who carry a gun, knife, or other such weapon. A 9898% confidence interval is desired where the interval is no wider than 5 percentage points?
(a) How many randomly selected students must be surveyed if we assume that there is no available information that could be used as an estimate of p^p^.
First Hint: note the question is limiting the "width" of the interval to 5 percentage points. Also, use at least five decimals places of accuracy with all values used in calculations. Your final answer however should be an integer.
Answer:
(b) How many randomly selected students must be surveyed if we assume that another study indicated that 66% of college students carry weapons. Answer:
A college student surveyed fellow students in order to determine a 90% confidence interval on the proportion of students who plan on voting in the upcoming student election for Student Government Association President. Of those surveyed, it is determined that 82 plan on voting and 169 do not plan on voting.
(a) Find the 90% confidence interval.
Enter the smaller number in the first box.
Confidence interval: ( , ).
In: Statistics and Probability
A political candidate has asked you to conduct a poll to
determine what percentage of people support her.
If the candidate only wants a 1% margin of error at a 99%
confidence level, what size of sample is needed?
Give your answer in whole people.
In: Statistics and Probability
Comfort Food Magazine states that the percentage of people who like to eat hot dogs is 55%. A random selection of 275 people are asked if they like eating hot dogs and 55% said they do. At the α = 0.09 level, is there sufficent evidence to conclude that the percentage of people that like to eat hot dogs is higher than 55%?
In: Statistics and Probability
For mallard ducks and Canada geese, what percentage of nests are successful (at least one offspring survives)? Studies in Montana, Illinois, Wyoming, Utah, and California give the following percentages of successful nests (Reference: The Wildlife Society Press, Washington, D.C.).
| x: Percentage success for mallard duck nests | ||||
| 86 | 53 | 86 | 44 | 32 |
| y: Percentage success for Canada goose nests | ||||
| 63 | 60 | 57 | 30 | 24 |
(a) Use a calculator to verify that Σx = 301; Σx2 = 20,561; Σy = 234; and Σy2 = 12,294.
| Σx | Σx2 | ||
| Σy | Σy2 |
(b) Use the results of part (a) to compute the sample mean,
variance, and standard deviation for x, the percent of
successful mallard nests. (Round your answers to two decimal
places.)
| x | |
| s2 | |
| s |
(c) Use the results of part (a) to compute the sample mean,
variance, and standard deviation for y, the percent of
successful Canada goose nests. (Round your answers to two decimal
places.)
| y | |
| s2 | |
| s |
(d) Use the results of parts (b) and (c) to compute the coefficient
of variation for successful mallard nests and Canada goose nests.
(Round your answers to one decimal place.)
| x | y | |
| CV | % | % |
Write a brief explanation of the meaning of these numbers. What do
these results say about the nesting success rates for mallards
compared to Canada geese?
a. The CV is the ratio of the standard deviation to the mean; the CV for Canada goose nests is higher.
b. The CV is the ratio of the standard deviation to the mean; the CV for Canada goose nests is equal to the CV for mallard nests.
c. The CV is the ratio of the standard deviation to the mean; the CV for mallard nests is higher.
d. The CV is the ratio of the standard deviation to the variance; the CV for Canada goose nests is higher.
e. The CV is the ratio of the standard deviation to the variance; the CV for Canada goose nests is equal to the CV for mallard nests.
g. The CV is the ratio of the standard deviation to the variance; the CV for mallard nests is higher.
Would you say one group of data is more or less consistent than the
other? Explain.
a. The x data group is more consistent because the standard deviation is smaller.
b. The two groups are equally consistent because the standard deviations are equal.
c. The y data group is more consistent because the standard deviation is smaller.
In: Statistics and Probability