HYPOTHESIS TESTING PRACTICE PROBLEMS
1) According to Consumer Expenditures, the average consumer spent $1729 on apparel and services in 2017. In 2018, a random sample of 36 consumers had a mean of $1667.11 and standard deviation of $351.69. Can it be said that at the 5% level of significance that the mean level of consumption differed in 2018 with respect to 2017?
2) Having a baby in a US Hospital costs $ 2528 on average. Active Management of Labor, (AML) is a group of interventions designed to help reduce the length of labor and of Caesarian Sections. With AML assistance, a random sample of 200 baby deliveries had a mean cost of $ 2480 with a standard deviation of $ 766. At the 5% level of significance, do the data provide sufficient evidence to conclude that AML reduces the cost of having a baby in a US Hospital?
3) In a study published by the American Journal of Psychiatry (May 2019) researchers wanted to measure the effect of alcohol on the hippocampal region of the brain in adolescents. 12 adolescents who use alcohol were randomly chosen. Hippocampal volumes were examined. The mean hippocampal volume for the whole population is 9.03 cubic centimeters. An analysis revealed that the mean hippocampal in the 12 chosen subjects was 8.1 cubic centimeters with a standard deviation of 0.7 cubic centimeters. At the 1% level of significance, can it be concluded that the adolescents have a lower hippocampal volume?
4) In 2015, the mean household expenditure for energy was $ 1493 according to data published by the US Energy Information Association. Pratap is an economist and he thinks that this has changed significantly in 2018. In a random sample of 35 households he found that the mean expenditure for energy was $1618 with a standard deviation of $321. At the 5 % level of significance can we agree with Pratap?
5) Acid rain from the burning of fossil fuels is worldwide concern. Researchers believe hat acid rain has caused many lakes from around the world to become acidic. A ake is classified as non-acidic if it has a pH level greater than 6. A recent study of 15 nountain lakes in Southern France revealed an average pH level of 6.6 with a tandard deviation of 0.672. Does a test at the 5 % level of significance provide esearchers with enough evidence to conclude that the lakes in Southern France are on-acidic?
6) The Venkanarasimarajuvaripeta Publishing Company collects information on the retail prices of books and is a respected and reliable publisher of its findings. Up until 2015, the mean retail price for all books was $ 43.50 with a standard deviation of $ 7.61. In 2018, retail prices for 40 randomly selected poetry books was $ 46.93. At the 1% significance level, do the data provide sufficient evidence to conclude that this year’s mean price of all poetry books has increased since 2015?
7) At the Pekawachnamaykoskwasayapinwansisko Pretzel Company a machine bags packages of pretzels with a total weight of 454 gr and a standard deviation of 7.8 gr. A random sample of 25 bags has a mean weight of 450 gr. If we test the machine at the 5% level of significance, can we conclude that the machine is not working properly?