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A)For small degrees of freedom, the curve displays right-skewness. b) As the degrees of freedom increase, the curve approaches a normal curve. c)  2 is.

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Presentation on theme: "A)For small degrees of freedom, the curve displays right-skewness. b) As the degrees of freedom increase, the curve approaches a normal curve. c)  2 is."— Presentation transcript:

1 a)For small degrees of freedom, the curve displays right-skewness. b) As the degrees of freedom increase, the curve approaches a normal curve. c)  2 is defined only for positive values of the variable. d) The area under a  2 curve is Which of the following is NOT true of the  2 probability density function? e) All of these are true about the  2 probability density function.

2 2) A regression of the amount of calories in a serving of breakfast cereal vs. the amount of fat gave the following results: Calories = Fat. Which of the following is a FALSE statement? a.It is estimated that for every additional gram of fat in the cereal, the number of calories increases by about 9. b. It is estimated that in cereals with no fat, the total amount of calories is about 97. c. If a cereal has 2 g of fat, then it is estimated that the total number of calories is about 115. d. If a cereal has about 145 calories, then this equation indicates that it has about 5 grams of fat. e. One cereal has 140 calories and 5 g of fat. Its residual is about 5 cal.

3 The two-way table specifies favorite ice cream flavors by gender. ChocolateVanillaStrawberry Male32143 Female16410 a)We have sufficient evidence of an association between gender and ice cream flavor preference at the 5% level. b) There is insufficient evidence of a relationship between gender and ice cream flavor preference. c) Since we are dealing with the two genders, a two-sample t-test is more appropriate. e) The information given is not sufficient to draw a conclusion. d) No conclusion, since a  2 test should not have been preformed due to assumption violations. 3. A  2 test of significance yields a test statistic of  2 = and a p-value of.005 with df = 2. Which of the following is a valid conclusion from this information?

4 4. A genetic model for offspring of two Labrador retrievers states: black: yellow: chocolate = 5:4:1. Two Labrador retrievers are bred and a litter consisting of 3 black dogs, 5 yellow dogs, and 2 chocolate dogs is produced. For a goodness of fit test, the  2 statistic would be: a)1.79c) 2.92 d) 4.94e) 7.08 b) 2.05

5 5. The spinner in a board game has eight colors the arrow can land on. To test the fairness results you spin the arrow 75 times: Green: 3Brown: 16 Blue: 13Yellow: 14 Red: 9White: 8 Orange: 9Black: 3 Calculate the chi-square statistic for these data and use a table to find the p- value. A.  ² = 14.07, p =.05 B.  ² = , p =.984 E.  ² = 9.04, p <.05 D.  ² = 9.04, p =.25 C.  ² = ,.02 > p >.01

6 6) The corn rootworm is a pest that can cause significant damage to corn, resulting in a reduction in yield and thus in farm income. A farmer will examine a random sample of plants from a field in order to decide whether or not the number of corn rootworms in the whole field is at a dangerous level. If the farmer concludes that it is, the field will be treated. The farmer is testing the null hypothesis that the number of corn rootworms is not at a dangerous level against the alternative hypothesis that the number is at a dangerous level. Suppose that the number of corn rootworms in the whole field actually is at a dangerous level. Which of the following is equal to the power of the test? (B) The probability that the farmer will decide not to treat the field. (C) The probability that the farmer will fail to reject the null hypothesis. (D) The probability that the farmer will reject the alternative hypothesis. (E) The probability that the farmer will not get a statistically significant result. (A) The probability that the farmer will decide to treat the field. On the test I will also ask about Type 1 and Type 2 errors!!

7 The following table displays by gender the number of people in a club who favor a particular political party. DemocraticRepublicanIndependent Female Male If we were to do a chi-square test, which expression would calculate correctly the expected frequency of the number of females who favor the Republican Party? b) c) d) e) a)

8 The following table displays by gender the number of people in a club who favor a particular political party. DemocraticRepublicanIndependent Female Male What is the probability that a person chosen at random will be female given the person favors the Democratic Party? b) 0.2c) d) e) a) 0.4

9 9. Your friend says she has an unfair die: the probability of getting a one or a six is 1/3 for each, and the probability of getting a two, three, four, or five is 1/12 for each. You want to test her statement. What is the minimum number of times you have to roll the die to use a chi- square goodness-of-fit test here? a) 5 b) 18 c) 39 e) 65 d) 60

10 10. A test of independence for data organized in a two-way table relating number of siblings and number of family relocations is conducted using the chi-square distribution. The p-value of the test is.045. If alpha is.05, then which of the following is a valid conclusion of the test? a)The mean is significant. b) We reject the hypothesis that the variables are dependent. c) We accept the hypothesis that the variables are independent. e) The variables are independent. d) We have sufficient evidence to reject the hypothesis that the variables are independent.

11 11) The table to the right provides data on sex, political party affiliation, and income bracket for a sample of people questioned during a poll. Group the bivariate data for the two variables "sex" and "income bracket" into a contingency table. Sex Political Party Income Bracket M Rep High F Dem Middle M Dem Low F Other Middle M Rep Low FRep High M RepHigh M Dem High F Rep Low M Dem High F Rep Middle F Dem Middle M Dem Middle M Rep Low F Dem High M Rep Low F Other High M Other Middle F Dem Low M Dem Middle M Rep Low FDemMiddle Answer choices are on next slide

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13 1)E2) E 3) D4) B 5) C6) A 7) A8) A 9) D10) D 11) D MC 3 rd Nine weeks test


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