Question

In: Statistics and Probability

A sociologist is studying the age of the population in Blue Valley. Ten years ago, the...

A sociologist is studying the age of the population in Blue Valley. Ten years ago, the population was such that 20% were under 20 years old, 14% were in the 20- to 35-year-old bracket, 34% were between 36 and 50, 24% were between 51 and 65, and 8% were over 65. A study done this year used a random sample of 210 residents. This sample is given below. At the 0.01 level of significance, has the age distribution of the population of Blue Valley changed? Under 20 20 - 35 36 - 50 51 - 65 Over 65 29 28 66 68 19 (i) Give the value of the level of significance. State the null and alternate hypotheses. H0: Ages under 20 years old, 20- to 35-year-old, between 36 and 50, between 51 and 65, and over 65 are independent. H1: Ages under 20 years old, 20- to 35-year-old, between 36 and 50, between 51 and 65, and over 65 are not independent. H0: Time ten years ago and today are independent. H1: Time ten years ago and today are not independent. H0: The population 10 years ago and the population today are independent. H1: The population 10 years ago and the population today are not independent. H0: The distributions for the population 10 years ago and the population today are the same. H1: The distributions for the population 10 years ago and the population today are different. (ii) Find the sample test statistic. (Round your answer to two decimal places.) (iii) Find or estimate the P-value of the sample test statistic. P-value > 0.100 0.050 < P-value < 0.100 0.025 < P-value < 0.050 0.010 < P-value < 0.025 0.005 < P-value < 0.010 P-value < 0.005 (iv) Conclude the test. Since the P-value ≥ α, we reject the null hypothesis. Since the P-value < α, we do not reject the null hypothesis. Since the P-value < α, we reject the null hypothesis. Since the P-value ≥ α, we do not reject the null hypothesis. (v) Interpret the conclusion in the context of the application. At the 1% level of significance, there is insufficient evidence to claim that the age distribution of the population of Blue Valley has changed. At the 1% level of significance, there is sufficient evidence to claim that the age distribution of the population of Blue Valley has changed.

Solutions

Expert Solution

a) level of significance =0.01

H0: The distributions for the population 10 years ago and the population today are the same. H1: The distributions for the population 10 years ago and the population today are different.

b)

applying chi square goodness of fit test:
           relative observed Expected residual Chi square
category frequency(p) Oi Ei=total*p R2i=(Oi-Ei)/√Ei R2i=(Oi-Ei)2/Ei
1 0.2000 29.0000 42.00 -2.01 4.024
2 0.1400 28.0000 29.40 -0.26 0.067
3 0.3400 66.0000 71.40 -0.64 0.408
4 0.2400 68.0000 50.40 2.48 6.146
5 0.0800 19.0000 16.80 0.54 0.288
total 1.000 210 210 10.9330
test statistic X2 = 10.933

iii)

0.025 < P-value < 0.050

iv)

Since the P-value ≥ α, we do not reject the null hypothesis.

v) At the 1% level of significance, there is insufficient evidence to claim that the age distribution of the population of Blue Valley has changed.


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