A researcher was interested in knowing whether the mean weight of the second bab

Question

A researcher was interested in knowing whether the mean weight of the second baby is higher, lower, or about the same as the mean weight of the first baby for women who have at least two children. She selected a representative sample of 40 women who had at least two children and asked them for the weights of the oldest two at birth. She found that the mean of the differences (first - second) was 5 ounces, and the standard deviation of the differences was 7 ounces. a. Why was the researcher's study design better than taking independent samples of mothers and asking the first sample about the weight of their first baby and the second sample about the weight of their second baby? b. Define the parameter of interest. Use appropriate notation. c. Write the mean of 5 ounces and the standard deviation of 7 ounces using appropriate statistical notation. d. Find a 90% confidence interval for the parameter that you defined in part (b). Write a sentence or two interpreting the interval. e. Draw a picture similar to Figure 11.9 on page 433 illustrating the confidence interval you found in part (d). Using this picture, would you conclude that the mean birth weights for the population are likely to differ?

Explanation / Answer

Answer:

By asking the equivalent mothers their first along with accord children's confinement weights, rather than two different independent sample of mothers, we are getting stability (less variability) in our data The same look after has genetically similar children, she had a similar pregnancy for both children (e.g., diet, fitness, medical care), and consequently her babies' weight difference will more likely address the underlying investigate question "Do first babies weigh more, less, or the same than second babies?

“If independent samples were taken, the variability inside the two groups of (=elated) birth weights would probably overshadow the crux of the research question

    (b) The limitation of interest m this study is p., the true mean dissimilarity [(first-born child's birth           weight) — (second child's birth weight)]. We want to know if the nude value is positive, negative, or 0.

(c) The sample statistics are d = 5 ounces for the example mean dissimilarity, and s, = 7 ounces for the sample standard divergence of the differences.

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