o 9.1 Sampling Distributions
o 9.2 Sample Proportions
o 93 Sample Means
o Chapter Review
Chapter 9 Sampling Distributions
The reasoning of statistical inference rests on asking, "How often would this
chapter 10 Introduction to Inference
Here are the results of'the z test: z = -1.449 and the P-value is O.Q7$;6;, .
10.2 Tests of significance :-:359-
10.2 TESTS O F SIGNIFICANCE
C onfidence intervals are one of the two most common types of statistical
inference. Use a confidence interval when your goal is to estimate a population parameter. T h e second common
10 Introduction to Inference
ACTIVITY 10 A Little Tacky!
Materials: Small box of thumbtacks
When you flip a fair coin, it is equally likely to land "heads" or "tails." Do
thumbtacks behave in the same way? In this activity, you will toss a thumbtac
10.1 (a) 44% to 50%. (b) We do not have information about the whole population; we only know about a small sample. We expect our sample to give us a good estimate of the population value, but it will not be exa
2.5003 is a parameter; x
7.2% is a statistic.
48% is a statistic; p
9.4 Both x1
335 and x2
2.5009 is a statistic.
52% is a parameter.
289 are statistics.
9.5 (a) Since the proportion of times the
8.1 (a) No: There is no fixed n (i.e., there is no definite upper limit on the number of defects). (b) Yes: It is reasonable to believe that all responses are independent (ignoring any "peer pressure"), and all
7.1 (a) P(less than 3) P(1 or 2)
2 6 1 3.
(b)(c) Answers vary.
7.2 (a) BBB, BBG, BGB, GBB, GGB, GBG, BGG, GGG. Each has probability 1/8. (b) Three of the eight arrangements have two (and only two) girls, so P(X
6.1 Long trials of this experiment often approach 40% heads. One theory attributes this surprising result to a "bottle-cap effect" due to an unequal rim on the penny. We don't know. But a teaching assistan
5.1 The population is employed adult women, the sample is the 48 club members who returned
5.2 (a) An individual is a person; the population is all adult U.S. residents. (b) An individual is a
4.1 (a) Since 2.54 cm 1 inch, inches are changed to centimeters by multiplying by 2.54. Letting
height in inches and y
height in centimeters, the transformation is y
2.54x, which is
3.1 (a) Time spent studying is explanatory; the grade is the response variable. (b) Explore the relationship; there is no reason to view one or the other as explanatory. (c) Rainfall is explanatory; crop
2.1 There are many correct drawings. Here are two possibilities:
2.2 (a) The area under the curve is a rectangle with height 1 and width 1. Thus the total area under
the curve 1 1 1.
(b) 20%. (The reg
1.1 (a) The individuals are vehicles (or cars). (b) The variables are: vehicle type (categorical),
transmission type (categorical), number of cylinders (quantitative), city MPG (quantitative), and
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