Download Introduction to Chance Models (Section 1.1) Introduction A key step

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Statistics wikipedia, lookup

History of statistics wikipedia, lookup

Transcript
Follow-ups:
1. A recent study classified children according to the type of lighting used in their room (full light,
night light, no light) and their eye condition (near-sighted, normal vision, and far-sighted). The
two-way table of counts is:
Full light Night light No light Total
Near-sighted
41
78
18
137
Normal vision
22
115
114
251
Far-sighted
12
39
40
91
Total
75
232
172
479
a) Is this an observational study or an experiment? Explain briefly.
b) What proportion of the children who slept in a room with full light were near-sighted?
The following segmented bar graph displays these data:
100%
80%
60%
Far-sighted
40%
Normal vision
Near-sighted
20%
0%
Full light
Night light
No light
c) Based on this graph, describe the association (if any) between lighting condition and
eyesight.
d) Provide an argument that parents’ eyesight could be a confounding variable in this study.
e) Would you conclude that this study provides strong evidence of a cause-and-effect
relationship between lighting condition and eyesight? Explain briefly.
2. In a study published in a 2007 issue of the journal Preventive Medicine, researchers found
that smokers were more likely to have used candy cigarettes as children than non-smokers
were. When hearing about this study, John said: “But isn’t the smoking status of the person’s
parents a confounding variable here?” When Karen asked what he meant, John said: “Children
whose parents smoke are more likely to become smokers themselves when they become
adults.” What else does John need to say in order to explain how the parents’ smoking status
can be a confounding variable in this study?
June 27, 2014
MAA PREP workshop
63