What is the minimum number of pairs needed to estimate the difference in the means of two populations using paired difference samples to within 3 units at 98% confidence given σd = 12.5?  105 77 95 91

For a population with a = 12, how large a sample is necessary to have a standard error that is less than 4 points? n > ?

7. A sample of size N= 123 adults randomly selected, spent 8.20 hr/ week on the internet with a standard deviation of 6=9.84 hr. Construct a Confidence Interval of 95% for the population mean U the population mean hours for the internet ?

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7. Suppose a researcher wants to estimate the difference in proportions of firstborn between the college graduates and non-graduates to within 0.05, with 90% confidence. How many college graduates and non-graduates must he interview, assuming that an equal number will be interviewed from each group?

Suppose 140 geology students measure the mass of an ore sample. Due to human error and limitations in the reliability of the balance, not all the readings are equal. The results are found to closely approximate a normal curve, with mean 85 g and standard deviation 2 g. Use the symmetry of the normal curve and the empirical rule as needed to estimate the number of students reporting readings between 81 g and 89 g. The number of students reporting readings between 81 g and 89 g is (Round to the nearest whole number as needed.)

6. In Roosevelt National Forest, the rangers took random samples of live a) aspen trees and measured the base circumference of each tree. A sample of 36 trees had a mean circumference of 15.71 inches and a population standard deviation of 4.63 inches. Find a 98% confidence interval for the mean circumference of all aspen trees in Roosevelt National Forest from this data. b) 16.475) inches. What confidence level was used to produce this interval? Suppose a confidence interval constructed from this data was (14.945,

It is desired to estimate the mean number of chocolate chips per cookie for a large national brand. How many cookies would have to be sampled to estimate the true mean number of chips per cookie within 2 chips with 98% confidence? Assume that o = 10.1 chips. Оп 3D 12 n = 239 O n = 139 n = 66

Suppose that we have a set of 1000 values with average 4, and standard deviation 3. (This is population data). a) The sum of the values of this set is b) The sum of squares of deviations from the average of the values is c) The sum of squares of the values is d) If the data has an empirical histogram, 7 is approximately the integer as the answer). th percentile (Give an The 97.5th percentile is approximately (Give an integer as the answer). e) If the histogram of the data is unknown, the (100 * ) th percentile is at most