A simple random sample of 50 items resulted in a sample mean of 25.1. The population standard deviation is 2.1. At 95% confidence, what is the margin of error? Hint: The sample size n=50>30, meaning that you can use the normal Z distribution and there's no need to use the t-distribution.

An investigator polls a representative sample of common cold sufferers, asking them to estimate the number of hours of physical discomfort caused by their most recent cold. Their estimates approximate a normal curve with a mean of 91 hours and a standard deviation of 23 hours. Show your z-score and p-value calculations.   Inverse Normal Distribution: What is the estimated number of hours for the shortest-suffering 20 percent?  Inverse Normal Distribution: A medical researcher wishes to concentrate on the 10 percent who suffered the most. To be included in this group, a patient would have suffered how many hours?

A biologist interested in estimating the correlation between the body mass ( in grams) and body length ( in cm) of porcupines has a random sample of 18 porcupines with r = 0.407. The bootstrap distribution she constructed in approximately normal and the standard error is estimated to be 0.165. use the normal distribution to construct and interpret a 98% confidence interval for the correlation between body mass and body length in porcupines. round all values to three decimal places.

A normal distribution has mean 55.955.9 and standard deviation 2.582.58. Find the data value corresponding to z equals negative 3.91z=−3.91.   The data value is enter your response here. ​(Round to the nearest tenth as​ needed.)

A doctor tests a claim that an average adult above 50 consumes no more than 3-1/2 pills per day.  Standard Dev is 0.7.  A sample of 45 adults avg 3.72 per day.  Test the claim. -Standard Dev of sample mean -Z-score for sample mean -P-Value

A hospital administrator believes that the standard deviation of the number of people using outpatient survey per day is greater than 8. A random sample of 15 days is selected. The data are shown below. At α = 0.1, is there enough evidence to support the administrator’s claim? Show your work and indicate the conclusion and assume that the variable is normally distributed.25, 30, 5, 15, 18, 42, 16, 9, 10, 12, 12, 38, 8, 14, 27.

The overhead reach distances of adult females are normally distributed with a mean of 202.5 cm and a standard deviation of 8 cm A. Find the probability that an individual distance is greater than 212.50 cm b. Find the probability that the mean for 25 randomly selected distance is greater than 201.20 C. why can a normal distribution be used in part b even though the sample size does not exceed 30?

The grade point average for ALL juniors at a large college has a standard deviation of 0.50.  A random sample of 20 students is to be used to estimate the population mean grade point average.  What condition do you need to verify prior to computing the probability of obtaining a sample mean within plus or minus 0.2 of the population mean?

Assume all populations are normally distributed. A travel analyst claims that the mean price of a round trip flight from New York City to Los Angeles is less than $507. In a random sample of 55 round trip flights from NYC to LA, the mean price is $502. Assume the population standard deviation is $111. At α = 0.05, is there enough evidence to support the travel analyst’s claim?

A normal distribution with a mean of 25 and a standard deviation of 5. What is the corresponding z score for a case having a value of 10?