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Scores on a test have a mean of 71 and the score of 80 falls at the 75th percentile. The scores have a distribution that is approximately normal. Find the score that falls at the 39th percentile. pl
The estimate of the population proportion is to be within plus or minus .04, with a 98 percent level of confidence. The best estimate of the population proportion is .25. How large a sample is requi
A company studying the productivity of their employees on a new information system was interested in determining if the age (x) of data entry operators influenced the number of completed entries mad
For example, the probability that the economy will be in "boom" state is 0.15. In this case, if you invest in the stock market your return is assumed to be 25%; on the other hand if you invest in go
A medical researcher wishes to determine the percentage of females who take vitamins. He wishes to be 95% confident that the estimate is within 2.5 percentage points of the true proportion. A recent
Wildlife biologists are attempting to track the prevalence of rabies in Texas coyota populations. They trap and test coyotes in three widely separated counties to determine whether the prevalence, t
A researcher is interested in estimating the percentage of US residents without health insurance. How large a sample is needed so that the maximum margin of error of a 95% confidence interval is no
It is believed 30% of all adults are overweight. How larger sample is necessary to estimate the true proportion of adults who are overweight with a 95% confidence interval so that the margin of erro
A blood test indicates the presence of a particulat disease 95% of the time when the disease is actually present. The same test indicates the presence of the disease 0.5% of the time when the dsease
A poll of 200 American adults showed that 144 though that chemical dumps are among the most serious environmental problems. Estimate with a 98% confidence interval the proportion of the population w
The mean and standard deviation of a random sample of size 20 trees are 30.2 feet and 4.3 feet, respectively. Find the 98% confidence interval for the mean height of trees in the forest. Give a verb
Find the t-critical value for given confidence level and the sample size.
A sample has a mean of 120 and a standard deviation of 20.0. Find the value x that corresponds to each of these standard scores. Use the following formula:
Assume the population standard deviation is 2.1 pounds. b. Physician thinks that the margin of error is too large. Estimate the sample size required to estimate the mean birth weight within 0.3 poun
A researcher is interested in estimating the mean length of walleye in a lake with a 95% confidence interval. Assuming the standard deviation of lengths is inches, estimate the sample size required
An experimenter compares two sets of measurements from indpendent samples:
GPA of SCSU students is normally distributed with standard deviation 0.8. The average GPA of a random sample of 25 students found to be 2.3. Find the 98% confidence interval for the mean GPA of all
Construct a histogram and a percentage polygon. Construct a cumalitve percentage distribution and plot a cumalative percentage polygon (ogive).
Suppose 250 people out a survey asking how many dogs and cats they own. The results are given in the following table, where the entry in row i and column j is the number of respon
A researcher records the level of attention among 18 students during an interactive and lecture portion of a single class. If she computes a related samples t-test at a .05 level of significance (tw
A random sample of size 100 is to be taken from a population that has a proportion equal to 0.35. The sample proportion will be used to estimate the population proportion.
A researcher uses analysis of variance to test for mean differences among four treatments with a sample of n = 8 in each treatment. The F-ratio for this analysis would have what df values?
A common test for extrasensory perception (ESP) asks subjects to identify which of four shapes (star, circle, wave, or square) appears on a card unseen by the subject.
Let P(x, y) be the probability of choosing an x-colored ball on the first draw and a y-colored ball on the second draw. Compute the probability for each outcome of the experiment.
Find the mean and the standard deviation for the population. Samples sizes of 2 will be drawn from the population. Use the answers in part a to calculate the expected value and the standard deviation