invest_3ed.pdf

# Technology to perform the calculations for these two

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Technology: To perform the calculations for these two-sample z -procedures you can use the Theory- Based Inference applet ( two proportions ) or Minitab ( Stat > Basic Statistics > 2 Proportions ) or iscamtwopropztest in R. Practice Problem 3.1B USA Today reported that newspapers appear to be losing credibility over time (March, 2004). They cited a nationwide sample of 1,002 adults, 18 years or older, interviewed via telephone (under the direction of Princeton Survey Research Associates) during the period May 6-16, 2002. Of the 932 respondents who were able to rate the daily newspaper they were most familiar with, 591 rated the paper as “largely believable” (a 3 or a 4 on the scale). When the same question was asked four years earlier (May 7 13, 1998), 922 said they could rate their daily paper and of those, 618 rated the paper as “largely believable.” (a) Are the technical conditions met to calculate the two-sample z -interval for these data? Explain. (b) Calculate and interpret a 95% confidence interval from these data.

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Chance/Rossman, 2015 ISCAM III Investigation 3.2 196 Investigation 3.2: Nightlights and Near-sightedness Myopia, or near-sightedness, typically develops during the childhood years. Recent studies have explored whether there is an association between development of myopia and the use of night-lights with infants. Quinn, Shin, Maguire, and Stone (1999) examined the type of light children aged 2-16 were exposed to. Between January and June 1998, the parents of 479 children who were seen as outpatients in a university pediatric ophthalmology clinic completed a questionnaire (children who had already developed serious eye conditions were excluded). One of the questions asked was “Under which lighting condition did/does your child sleep at night?” before the age of 2 years. The following two- way table classifies the children’s eye condition and whether or not they slept with some kind of light (e.g., a night light or full room light) or in darkness. Some light Darkness Total Near-sighted 188 18 206 Not near-sighted 119 154 273 Total 307 172 479 Definition: When we have two variables, we often specify one to be the explanatory variable and the other to be the response variable . The explanatory variable is the one that we think might be influencing or explaining changes in the response variable, the outcomes of interest. (a) Which variable, lighting condition or eye condition, would you consider the explanatory variable in this study and which the response variable? (b) Calculate conditional proportions to measure the difference in the rate of near sightedness between the children with and without lighted rooms in this sample. (Use appropriate symbols.) Also produce a segmented bar graph to compare the eye condition of the two lighting groups. Comment on what this graph reveals about differences in eye condition between these lighting groups. Do you think this difference will be statistically significant? Explain.
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