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Study design Answers
To find:Whether the experiment is an observational or a designed experiment.
A proposed study design is to leave 100 questionnaires by the checkout line in a student cafeteria. The questionnaire can be picked up by any student and returned to the cashier. Explain why this volunteer sample is a poor study design.
In the 1970s a study was conducted in Philadelphia in which 500 cases were randomly assigned to treatments for the common cold: 250 subjects received the medication and 250 received a placebo. A total of 383 patients improved within 24 hours. Of those who received the medication 241 improved within 24 hours and of those who received the placebo 142 improved within 24 hours. A test of significance was conducted on the following hypotheses.
: The rates for the two treatments are equal.
: The treatment of medication has a higher improvement rate.
This test resulted in a p-value of 0.0761.
a.) Interpret what this p-value measures in the context of this study.
b.) Based on this p-value and study design, what conclusion should be drawn in the context of this study? Use a significance level of
c.) Based on your conclusion in part (b), which type of error, Type I or Type II, could have been made? What is one potential consequence of this error?
The Centers for Disease Control reported the percentage of people 18 years of age and older who smoke (CDC website, December 14, 2014). Suppose that a study designed to collect new data on smokers and nonsmokers uses a preliminary estimate of the proportion who smoke of .30.
a. How large a sample should be taken to estimate the proportion of smokers in the population with a margin of error of .02? Use 95% confidence.
A study of young children was designed to increase their intake of whole-grain, rather than regular-grain, snacks. At the end of the study, the 79 children who participated in the study were presented with a choice between a regular-grain snack and a whole-grain alternative. The whole-grain alternative was chosen by 55 children. You want to examine the possibility that the children are equally likely to choose each type of snack.
Perform the significance test. (Use
. Round your test statistic to two decimal places and your P-value to four decimal places.)
A correlational study is designed to?
a) assess the association between two interval measures.
b) assess the association between two categorical variables
c) compare the means of three or more groups
d) manipulate the independent variables
In the middle of the design, she decided to add the following line segment. How would she name this line segment?
___ or ___
The Centers for Disease Control reported the percentage of people 18 years of age and older who smoke
. Suppose that a study designed to collect new data on smokers and nonsmokers uses a preliminary estimate of the proportion who smoke of .30.
a.How large a sample should be taken to estimate the proportion of smokers in the population with a margin of error of .02(to the nearest whole number)? Use 95% confidence.
b.Assume that the study uses your sample size recommendation in part(a) and finds 520 smokers. What is the point estimate of the proportion of smokers in the population(to 4 decimals)?
c.What is the 95% confidence interval for the proportion of smokers in the population (to 4 decimals)?
Is wrapping a banana in plastic wrap and leaving the other bananas alone to see which one rots faster and experimental study design or and observational study design?
To explain: whether the given study on male health professional is an observational study with a cohort design, an observational study with case-control design or an experiment
With the aid of examples briefly explain the difference between fixed effect and random effects models in experimental design.
Participants enter a research study with unique characteristics that produce different scores from one person to another. For an independent-measures study, these individual differences can cause problems. Identify the problems and briefly explain how they are eliminated or reduced with a repeated-measures study. Independent-measures study is used in the study.
Whether the given study depicts an observational study or a designed experiment and to identify the response variable.
The study is conducted to compare the battery lives of a brand-name battery and a generic plain-label battery in digital cameras. For this purpose, 30 digital cameras are randomly selected and divided into 2 groups, one of the groups uses the brand-name battery while the other one uses the generic plain-label battery. In both the cameras, pictures are taken under identical conditions by keeping all variables, except the battery-type, in control.
Whether confounding is an issue with this study or not.
Whether the given study depicts an observational study or an experiment.
The study involved 250 large-mouth bass in a lake. The 250 large-mouth bass were netted by conservation agents and were observed to determine how many of them were carrying parasites.
Know these terms. Explain in one sentence each what “randomized,” “double-blind,” and “placebo-controlled” mean in the description of the design of the study.
Experiment basics. Identify the subjects, the explanatory variable, and several response variables for this study.
The two response variables and whether they are qualitative or quantitative.
To find:The factors and the factor levels.
To explain:The assumptions for the test.
To explain:The explanatory variable in the study and determine whether it is a qualitive variable or quantitative variable.
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