The marketing research company comScore, Inc. reported that 65% of online searches in March 2010 used Google as the search engine. A network administrator wants to determine whether the percentage of searches that use Google is different in his company. He samples 400 searches and finds that 295 of them use Google. Can he conclude that the percentage of searches that use Google in his company differs from 65%? Use the α= 0.05 level of significance.
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The marketing research company comScore, Inc. reported that 65% of online searches in March 2010 used Google as the search engine. A network administrator wants to determine whether the percentage of searches that use Google is different in his company. He samples 400 searches and finds that 295 of them use Google. Can he conclude that the percentage of searches that use Google in his company differs from 65%? Use the α= 0.05 level of significance.
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- Tardigrades, or water bears, are a type of micro-animal famous for their resilience. In examining the effects of radiation on organisms, an expert claimed that the amount of gamma radiation needed to sterilize a colony of tardigrades no longer has a mean of 900 Gy (grays). (For comparison, humans cannot withstand more than 10 Gy .) A study was conducted on a sample of 27 randomly selected tardigrade colonies, finding that the amount of gamma radiation needed to sterilize a colony had a sample mean of 907 Gy , with a sample standard deviation of 17 Gy . Assume that the population of amounts of gamma radiation needed to sterilize a colony of tardigrades is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 0.05 level of significance, to support the claim that μ , the mean amount of gamma radiation needed to sterilize a colony of tardigrades, is not equal to 900…Tardigrades, or water bears, are a type of micro-animal famous for their resilience. In examining the effects of radiation on organisms, an expert claimed that the amount of gamma radiation needed to sterilize a colony of tardigrades no longer has a mean of 900 Gy (grays). (For comparison, humans cannot withstand more than 10 Gy .) A study was conducted on a sample of 27 randomly selected tardigrade colonies, finding that the amount of gamma radiation needed to sterilize a colony had a sample mean of 907 Gy , with a sample standard deviation of 17 Gy . Assume that the population of amounts of gamma radiation needed to sterilize a colony of tardigrades is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 0.05 level of significance, to support the claim that μ , the mean amount of gamma radiation needed to sterilize a colony of tardigrades, is not equal to 900…Tardigrades, or water bears, are a type of micro-animal famous for their resilience. In examining the effects of radiation on organisms, an expert claimed that the amount of gamma radiation needed to sterilize a colony of tardigrades no longer has a mean of 1350 Gy (grays). (For comparison, humans cannot withstand more than 10 Gy .) A study was conducted on a sample of 18 randomly selected tardigrade colonies, finding that the amount of gamma radiation needed to sterilize a colony had a sample mean of 1375 Gy , with a sample standard deviation of 75 Gy . Assume that the population of amounts of gamma radiation needed to sterilize a colony of tardigrades is approximately normally distributed. Complete the parts below to perform a hypothesis test to see if there is enough evidence, at the 0.05 level of significance, to support the claim that μ , the mean amount of gamma radiation needed to sterilize a colony of tardigrades, is not equal to 1350 Gy .
- . A taxi company has been using Brand A tires, and the distribution of kilometers to wear-out has been found to be approximately normal with mean =114,000 and σ = 11,600. Now it tries 12 tires of Brand B and finds a sample mean 117,200. Test at the 5% level of significance to see whether there is a significant difference (positive or negative) in kilometers to wear-out between Brand A and Brand B. In the problem above, if the true kilometers to wear-out is 114,000, what is the 95% confidence interval for sample means? First show how to get the critical z values.A large manufacturing company investigated the service it received from its suppliers and discovered that, in the past, 41% of all material shipments were received late. However, the company recently installed a just-in-time system in which suppliers are linked more closely to the manufacturing process.A random sample of 150 deliveries since the just-in-time system was installed reveals that 29 deliveries were late. If we want to test whether the proportion of late deliveries was reduced significantly at α = 0.10. Calculate the null and alternative hypothese.A large manufacturing company investigated the service it received from its suppliers and discovered that, in the past, 44% of all material shipments were received late. However, the company recently installed a just-in-time system in which suppliers are linked more closely to the manufacturing process. A random sample of 170 deliveries since the just-in-time system was installed reveals that 34 deliveries were late. If we want to test whether the proportion of late deliveries was reduced signicantly at = 0:01 the null and alternative hypotheses are a. Null hypothesis (H0) b. Alternative hypothesis (HA)
- A community college professor is interested in determining the relationship between the number of posts students make on Schoology and their respective grades. He planned to correlate the results from a sample from all his classes, however, due to time constraints, he decided to sample only from students with high grades. As his statistical consultant, state whether or not you support his plans and why.Why should we perform an ANOVA rather than multiple t-tests when we have three or more levels of our factor?The director of an obesity clinic in a large northwestern city believes that drinking soft drinks contribute to obesity in children. To determine whether a relationship exists between these two variables, she conducts the following pilot study. Eight- 12-year-old male volunteers are randomly selected from children attending a local junior high school. Parents of the children are asked to monitor the number of soft drinks consumed by their child over a one week period. The children are weighed at the end of the week and their weights converted into body mass index (BMI) values. The BMI is a common index used to measure obesity and takes into account both height and weight. An individual is considered obese if they have a BMI value 30. The following data or collected: child. # of soft drinks consumed BMI 1 3 20 2 1 18 3…
- Rosner analyzed data from children who lived near a lead smelter (which is a facility that uses extreme heat to extract the metal lead from lead ore) in El Paso, Texas, and reported that out of 124 children studied, 23 developed colic (which is a pattern of fussiness and crying for no apparent reason). Suppose that in the state of Taxes in general at the time (early 1980s), the rate of colic in children was 16.0%. Follow the steps for testing whether the proportion of children developing clico was significantly different for the 124 children living near the lead smelter than for Taxes children in general (16%). Use alpha level of 0.03 a. Identify the null hypothesis for this statistical test. b. Identify the alternative hypotheses for this statistical test. c. Explain: Why should this be a two-tailed test, the way I have described it? d. calculate the sample proportion p̂, rounded to three decimal places. e. Calculate the appropriate test statistic, show all work. f. Based on…Historically, the proportion of students entering a university who finished in 4 years or less was 65%. To test whether this proportion has decreased, 150 students were examined and 58% had finished in 4 years or less. At the 5% level of significance, does it appear the proportion has decreased from its historical level? To determine whether the proportion of students who finish in 4 year or less has statistically significantly decreased, what is the null and alternative hypothesis?A researcher hypothesizes that the lowering in cholesterol associated with weight loss is really due to exercise. To test this, the researcher carefully controls for exercise while comparing the cholesterol levels of a group of subjects who lose weight by dieting with a control group that does not diet. The difference between groups in cholesterol is not significant. Can the researcher claim that weight loss has no effect?