A tool company claims that the mean number of defective screws they produce per box is 72. The mean number of defective screws in 100 randomly chosen boxes was found to be 76, with a standard deviation of 19. Test this hypothesis.
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A tool company claims that the mean number of defective screws they produce per box is 72. The mean number of defective screws in 100 randomly chosen boxes was found to be 76, with a standard deviation of 19. Test this hypothesis.
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- Dean Halverson recently read that full-time college students study 20 hours each week. She decides to do a study at her university to see if there is evidence that students study an average of less than 20 hours each week. A random sample of 30 students were asked to keep a diary of their activities over a period of several weeks. It was found that he average number of hours that the 30 students studied each week was 18.7 hours. The sample standard deviation of 3.4 hours. Find the p-value. The p-value should be rounded to 4-decimal places.Fran is training for her first marathon, and she wants to know if there is a significant difference between the mean number of miles run each week by group runners and individual runners who are training for marathons. She interviews 42 randomly selected people who train in groups and finds that they run a mean of 47.1 miles per week. Assume that the population standard deviation for group runners is known to be 4.4 miles per week. She also interviews a random sample of 47 people who train on their own and finds that they run a mean of 48.5 miles per week. Assume that the population standard deviation for people who run by themselves is 1.8 miles per week. Test the claim at the 0.01 level of significance. Let group runners training for marathons be Population 1 and let individual runners training for marathons be Population 2. Step 2 of 3 : Compute the value of the test statistic. Round your answer to two decimal places.A sports writer wants to see if a football filled with helium travels farther, on average, than a football filled with air. 12 footballs were filled with helium to the recommend pressure and 15 footballs were filled with air to the recommended pressure. The mean yardage for the helium filled footballs was 267 yards with a standard deviation of 3 yards. The mean yardage for the air filled footballs was 241 yards with a standard deviation of 5 yards. Assume the populations are normal with equal variances. (a). Construct a 99% confidence interval for the mean difference in in yardage for the two types of footballs Lower bound (use 3 decimal places) Upper bound (use 3 decimal places) (b). What can you conclude about the sports writer's idea that helium footballs travel farther, on average? The helium footballs are no different than the other footballs, on average The other footballs travel farther on average than the helium footballs The helium footballs travel farther on average than the…
- A local church parish wants to raise money to add to their campus. In a sample from a previous fund raising campaign, the parish found that of the 131 people in the sample they contacted, that 69 actually contributed money. Of those that contributed money, the average contribution was $857 with a standard deviation of $265. In the recent fundraising campaign, a sample of 95 people revealed that 48 have contributed money with an average contribution of $1109 and a standard deviation of $339. When testing (at the 5% level of significance) whether the average amount contributed has increased in the current campaign compared to the previous campaign, what is the test statistic? (please round your answer to 2 decimal places)A nurse is interested in the amount of time patients spend exercising per day. According to a recent study, the daily workout time per adult follows an approximately normal distribution with a mean of 94 minutes and a standard deviation of 27minutes. If the nurse randomly samples patients in her office to analyze their exercise time and gets a standard error of 3minutes, how many patients did she sample?An engineer is going to redesign an ejection seat for an airplane. The seat was designed for pilots weighing between 140lb and 181lb. The new population of pilots has normally distributed weights with a mean of 150 lb and a standard deviation of 34.8 lb.
- Rhys is a quality control manager at a facility that manufactures snack foods. He is interested in the number of whole mini- pretzels that are in the 10 oz bags in the latest lot produced. Rhys selects 24 bags of mini-pretzels at random from the latest lot and counts the number of pretzels in each bag His sample has a mean of 158 pretzels with a standard deviation of 1.6 pretzels. What is the margin of error with 95% confidence (2 = 2.07)? O 0.02 O 66.76 O 0.68 O 6.34A fruit grower wants to test a new spray that a manufacturer claims will reduce the loss due to insect damage. She sprays 20 trees with the new spray and 20 trees with the standard spray. The following data were recorded: New Spray Standard Spray Mean yield per tree(lb) 240 227 Standard deviation 31.3 28.6 Do the data provide evidence that the new spray increases the yield per tree?According to the Insurance Association in US, the average annual expenditure for automobile insurance is $605. Suppose that in a simple random sample of 80 residents of New York, for most recent year their average expenditure was $638.62 with the standard deviation of $106.05. Based on these data, examine whether the average annual insurance for motorists in New York might be different from that in national level. Using the 0.05 level of significance, what conclusion do you reach? Also, construct and interpret 95% confidence interval for the population mean. Is the hypothesized mean within the interval? Is this consistent with the findings of the hypothesis test conducted?
- A sports writer wished to see if a football filled with helium travels farther, on average, than a football filled with air. To test this, the writer used 18 adult male volunteers. These volunteers were randomly divided into two groups of nine men each. Group 1 kicked a football that was filled with helium to the recommended pressure. Group 2 kicked a football that was filled with air to the recommended pressure. The mean yardage for Group 1 was ?¯1=300 yards with a standard deviation of ?1=8 yards. The mean yardage for Group 2 was ?¯2=296 yards with a standard deviation of ?2=6 yards. Assume the two groups of kicks are independent. Let ?1 and ?2 represent the mean yardage we would observe for the entire population represented by the volunteers if all members of this population kicked, respectively, a helium‑filled football and an air‑filled football. Assuming two‑sample ? procedures are safe to use and using Option 1 for the degrees of freedom, a 90% confidence interval for ?1−?2 is:…A plant manager is concerned her equipment may need recalibrating. It seems that the actual weight of the 19 oz cereal boxes it fills has been fluctuating. The equipment needs to be recalibrated if the standard deviation exceeds 0.7 oz. In order to determine if the machine needs to be recalibrated, 71 randomly selected boes of cereal from the next day's production were weighted. the standard deviation of the 71 boxes was 0.78. Using a = 0.1, determine if the machine needs to be recalibrated. Ho:o?: H:0ʻ Select an answer df = P-value = The p-value is... greater than a less than (or equal to) a This test statistic leads to a decision to... fail to reject the null accept the null accept the alternative reject the null As such, the final conclusion is that there Select an answer v sufficient evidence to conclude the standard deviation in cereal box weight is Select an answer than Select an answerA bottled water distributor wants to determine whether the mean amount of water contained in 1-gallon bottles purchased from a nationally known water bottling company is actually 1 gallon. You know from the water bottling company specifications that the standard deviation of the amount of water is 0.02 gallon. You select a random sample of 50 bottles, and the mean amount of water per 1-gallon bottle is 0.992 gallon. What is the test statistic?
