Travel times to work for people living in a city are normally distributed. 20 % of the travel times are greater than 60 minutes and 50 % of the travel times are below 25 minutes. What is the approximate standard deviation of the travel time to work for people living in this city?

The results of a common standardized test used in psychology research is designed so that the population mean is 175 and the standard deviation is 20. A subject earns a score of 227. What is the z-score for this raw score? Do not round your answer.z-score =    ?

Assume that adults have IQ scores that are normally distributed with a mean of 100 and a standard deviation 20. Find Upper P 4 which is the IQ score separating the bottom 44​% from the top 96​%.

A large chemistry course took their final exam. The mean was 75 with a standard deviation of 8. What are the exam scores that separate the top and bottom 5 percent of the class (extreme 10%)?                             What are the exams scores that separate the middle 10% of the class (5% on each side of the mean)?                             What proportion of people scored in the A range (90 or above)?                       What proportion of people failed the exam (60 or belo

If the mean snowfall for Ottawa Ontario Canada is 98 inches per year and the standard deviation is 25 inches what percentage of the time does Ottawa receive less than 125 inches of snow?

A right skewed data set has a mean of 35 and a standard deviation of 25. What can be said about the amount of data contained within the interval (-15, 85)?   95% of the data is within this range   68% of the data is within this range   Nothing   At least 75% of data is within this range

Marjorie More Mileage is obsessed with getting the best gas mileage possible for her 2017 Toyota Prius. She learns from the official Toyota web site that the official average mileage for all 2017 Prius is = 58.2 mpg with a standard deviation of = 1.2 mpg. Marjorie purchased a set of “hyper mileage” tires on-line that are supposed to improve gas mileage. For the next 100 fill ups, Marjorie noticed an average gas mileage of = 58.5 mpg. Help Marjorie perform a hypothesis test at a 1% level of significance to determine if her new tires actually improved her gas mileage.   What is the null hypothesis? What is the alternate hypothesis? Is this a left tail, right tail, or two tail test? Calculate the test statistic. State your conclusion.

1) After 5 pts were added to every score in a sample the mean is found to be 62 and the standard deviation is 12. What were the values for the mean and SD before the change? Explain

The red blood cell counts (in 105 cells per microliter) of a healthy adult measured on 6 days are as follows. 55, 53, 52, 51, 48, 53 Send data to calculator Find the standard deviation of this sample of counts. Round your answer to two decimal places.

According to a gallup survey of boys 77% of boys had played computer games in the past week compared to 65% of girls. You take and SRS of 104 boys and 120 girls\ Would it be reasonable to use the standard deviation formula?