# Mean and standard deviation

by | Sep 4, 2021 | Homework Help

1. A random sample of 1096 teenagers (ages 12 to 17) were asked whether they played games online; 778 said that they did.What is the value (±0.001) of the statistic p? 2. A study of commuting times reports the travel times to work of a random sample of 20 employed adults in Chicago. The mean is x¯= 26.15 minutes and the standard deviation is s = 18.04 minutes. What is the standard error (±0.0001) of the mean?3. A class survey in a large class for first-year college students asked, “About how many hours do you study in a typical week?”. The mean response of the 449 students was x¯ = 13 hours. Suppose that we know that the study time follows a Normal distribution with standard deviation 8 hours in the population of all first-year students at this university.What is the 99% confidence interval (± 0.001) for the population mean?Confidence interval is from _____  to _____  hours.4. In a randomized comparative experiment on the effect of color on the performance of a cognitive task, researchers randomly divided 66 subjects (26 males and 40 females ranging in age from 17 to 25 years) into three groups. Participants were asked to solve a series of 6 anagrams. One group was presented with the anagrams on a blue screen; one group saw them on a red screen; and one group had a neutral screen. The time, in seconds, taken to solve the anagrams was recorded. The paper reporting the study gives x¯=11.66 and s=4.53 for the times of the 26 members of the neutral group. (Give your answer to three decimal places.)A 96 % confidence interval for the mean time in the population from which the subjects were recruited is from _____ to _____  seconds.5. (multiple choice for the following) What critical value t* from Table C would you use for a confidence interval for the mean of the population in each of the following situations?I. A 98 % confidence interval based on n= 10 observations.a) 2.821b) 2.398c) 2.359d) 2.764II. An 80 % confidence interval from a sample of size 7.a) 1.282b) 1.415c) 1.397d) 1.4406. What t* value would you use to construct a 99% confidence interval with n = 12?7. What t* value would you use to construct a confidence interval with n = 25 at 90% significance?

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