8.4 Notes Estimating &. How can we tell the difference between two populations? I.e. How much longer does one brand of battery last than another? Use.

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8.4 Notes Estimating &

How can we tell the difference between two populations? I.e. How much longer does one brand of battery last than another? Use 2Samp Int under stat- test – Use z int if – Use t int if - Use 2Propz int if

Ex. 1 Suppose you are a biologist studying data from Yellowstone streams. A random sample of fishing reports in the years 1983 to 1988 (before a major fire) showed that the average catch per day was trout with pop. standard deviation. Then another random sample of fishing reports in the years 1990 to 1993 (after the fire) showed that the average catch per day was with pop. standard deviation. A) Find a 95% confidence interval for

b) Explain the meaning of this interval in context of this problem. There are three possible results for intervals for 1(–, –) : indicates that 2(+, +) : indicates that 3(–, +) : indicates that

Ex. 2 In his book, Professor Borbely comments that alcohol is a poor sleep aid. Suppose that a random sample of 29 college students was randomly divided into two groups. The first group of 15 people was given ½ liter of red wine before they went to sleep. The second group of 14 people was given no alcohol before going to sleep. The brainwave activity for each group is as follows (rapid waves indicates wakefulness): a)What must be assumed in this problem? b) Find a 90% confidence interval for

c) Explain the meaning of this interval in context of the problem. Ex. 3 Suppose that two groups of people are randomly selected to participate in a sleep study. In group I, the subjects spent 1 hour watching a comedy movie before going to sleep. In this group there were a total of 175 dreams recorded in which 49 of them were “bad” dreams (feelings of anxiety, fear, or aggression). In group II, the subjects did not watch a movie but simply went to sleep. In this group there were a total of 180 dreams recorded in which 63 of them were “bad” dreams (feelings of anxiety, fear, or aggression). a)Are both groups able to be considered as independent binomial normal distributions? Explain.

b) Compute a 95% confidence interval for c) Explain the meaning of this interval in context of this problem.

Assignment Day 1 p. 377 # 4-6, 7, 9, 11, Assignment Day 2 p. 379 # 10, 19, 20, 22-25