asked 2020-11-29

State whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case.

The Salk Vaccine. In the 1940s and early 1950s, the public was greatly concerned about polio. In an attempt to prevent this disease, Jonas Salk of the University of Pittsburgh developed a polio vaccine. In a test of the vaccine’s efficacy, involving nearly 2 million grade-school children, half of the children received the Salk vaccine, the other half received a placebo, in this case an injection of salt dissolved in water. Neither the children nor the doctors performing the diagnoses knew which children belonged to which group, but an evaluation center did. The center found that the incidence of polio was far less among the children inoculated with the Salk vaccine. From that information, the researchers concluded that the vaccine would be effective in preventing polio for all U.S. school children, consequently, it was made available for general use.

The Salk Vaccine. In the 1940s and early 1950s, the public was greatly concerned about polio. In an attempt to prevent this disease, Jonas Salk of the University of Pittsburgh developed a polio vaccine. In a test of the vaccine’s efficacy, involving nearly 2 million grade-school children, half of the children received the Salk vaccine, the other half received a placebo, in this case an injection of salt dissolved in water. Neither the children nor the doctors performing the diagnoses knew which children belonged to which group, but an evaluation center did. The center found that the incidence of polio was far less among the children inoculated with the Salk vaccine. From that information, the researchers concluded that the vaccine would be effective in preventing polio for all U.S. school children, consequently, it was made available for general use.

asked 2021-07-02

Do piano lessons improve the spatial-temporal reasoning of preschool children? A study designed to investigate this question measured the spatial-temporal reasoning of a random sample of 34 preschool children before and after 6 months of piano lessons. The differences (After - Before) in the reasoning scores have mean 3.618 and standard deviation 3.055.

asked 2021-06-18

Who is more likely to binge drink—male or female college students? The Harvard School of Public Health surveys random samples of male and female undergraduates at four-year colleges and universities about whether they have engaged in binge drinking. What type of study design is being used to produce data?

asked 2021-06-01

Determine whether the study depicts an observational study or a designed experiment. Identify the response variable in each case. A sport s report er asks 100 baseball fans if Barry Bonds's 756th homerun ball should be marked with an asterisk when sent to the Baseball Hall of Fame.

asked 2021-08-14

You have been given the task of designing a study concerning the lifetimes of five different types of electric motor. The initial question to be addressed is whether there are differences in mean lifetime among the five types. There are 20 motors, four of each type, available for testing. A maximum of five motors can be tested each day. The ambient temperature differs from day to day, and this can affect motor lifetime. a. Describe how you would choose the five motors to test each day. Would you use a completely randomized design? Would you use any randomization at all? b. If Xij

represents the measured lifetime of a motor of type i tested on day j, express the test statistic for testing the null hypothesis of equal lifetimes in terms of the Xij.

represents the measured lifetime of a motor of type i tested on day j, express the test statistic for testing the null hypothesis of equal lifetimes in terms of the Xij.

asked 2021-06-24

State whether the investigation in question is an observational study or a designed experiment. Justify your answer in each case. The National Association of Colleges and Employers (NACE) compiles information on salary offers to new college graduates and publishes the results in Salary Survey.

asked 2021-10-08

a. factors

b. factor levels

c. blocks

d. experimental unit

e. measurement unit

f. replications

g. treatments

\(\begin{matrix} \text{Pipe No} & \text{Plant} & {Temperature ( ^ { \circ } \mathbf { F } )} & \text{Hardener}\\ \text{1} & \text{1} & \text{200} & H_{1}\\ \text{2} & \text{1} & \text{175} & H_{2}\\ \text{3} & \text{2} & \text{200} & H_{1}\\ \text{4} & \text{2} & \text{175} & H_{2}\\ \text{5} & \text{1} & \text{200} & H_{1}\\ \text{6} & \text{1} & \text{175} & H_{2}\\ \text{7} & \text{2} & \text{200} & H_{1}\\ \text{8} & \text{2} & \text{175} & H_{2}\\ \text{9} & \text{1} & \text{200} & H_{3}\\ \text{10} & \text{1} & \text{175} & H_{3}\\ \text{11} & \text{2} & \text{200} & H_{3}\\ \text{12} & \text{2} & \text{175} & H_{3}\\ \text{13} & \text{1} & \text{200} & H_{3}\\ \text{14} & \text{1} & \text{175} & H_{3}\\ \text{15} & \text{2} & \text{200} & H_{3}\\ \text{16} & \text{2} & \text{175} & H_{3}\\ \text{17} & \text{1} & \text{200} & H_{2}\\ \text{18} & \text{1} & \text{175} & H_{1}\\ \text{19} & \text{2} & \text{200} & H_{2}\\ \text{20} & \text{2} & \text{175} & H_{1}\\ \text{21} & \text{1} & \text{200} & H_{2}\\ \text{22} & \text{1} & \text{175} & H_{1}\\ \text{23} & \text{2} & \text{200} & H_{2}\\ \text{24} & \text{2} & \text{175} & H_{1}\\ \end{matrix}\)