Which Supermarket Has the Lowest Prices in Town? All Claim

question 34

Multiple Choice

Which supermarket has the lowest prices in town? All claim to be cheaper, but an independent agency recently was asked to investigate this question. The agency randomly selected 100 items
Common to each of two supermarkets (labeled A and B) and recorded the prices charged by each
Supermarket. The summary results are provided below:
$$\begin{array} { l l r } \bar { x } \mathrm {~A} = 2.09 & \bar { x } \mathrm {~B} = 1.99 & \bar { d } = .10 \\\mathrm {~s} _ { \mathrm { A } } = 0.22 & \mathrm {~s} _ { \mathrm { B } } = 0.19 & s _ { d } = .03\end{array}$$
Assuming a matched pairs design, which of the following assumptions is necessary for a confidence interval for the mean difference to be valid?

• A) None of these assumptions are necessary.
• B) The samples are randomly and independently selected.
• C) The population variances must be equal.
• D) The population of paired differences has an approximate normal distribution.

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Definitions:

ABAB Design

A research method involving repeated measurements over time where conditions are alternated to observe the effect of an intervention.

Single-subject Experiment

A research design in which interventions are tested on a single individual, allowing for detailed observation of effects over time and control over variables affecting the outcome.

Developmental Study

A research approach that investigates how behavior changes and grows across the life span, often emphasizing growth patterns and fundamental changes.

Epidemiological Study

Research that seeks to investigate the patterns, causes, and effects of health and disease conditions in defined populations.