A simple random sample of 800 persons is taken to estimate the percentage of Independent voters among

Fantastic news! We've Found the answer you've been seeking!

Question:

A simple random sample of 800 persons is taken to estimate the percentage of Independent voters among 55,000 eligible voters in a certain town. It turns out that 349 people in the sample are Independents. Find a 95%-confidence interval for the percentage of Independents among the eligible voters in the town. Also, test the null hypothesis that p is equal to .3 at the .05 level. Interpret and compare the two approaches.

When it comes to making the correct causal inference the comparison of intact groups can be problematic. Consider a situation in which a Magnet School W shows a larger average science achievement score than the adjacent public school X. The magnet school claims that this increase in science scores is due to their superior teaching. What information would you like to have before you agree with their statement? 6. A psychologist has developed a set of activities which she hopes will help children develop better coping skills. In a study of the effectiveness of these activities, one class of second grade children practices these activities. Another class of second grade children serves as the control, and is not taught the activities. After some period of time, the coping skills of all of these children were assessed. A summary of these data is: n mean std. deviation Activities class: 41 55.48 14.01 No Activities class: 43 41.52 17.15 a. Test the hypotheses that the training made no difference. Set alpha to .05. Specify the null and alternative. b. Construct a 95% confidence interval for the difference between the two population means and compare it to the test of hypothesis. c. Would you consider this to be a true experiment? Explain. 7. An employer is concerned with the concurrent validity of a test. She decides to collect data on a random sample of 15 employees.

Using the data below assuming that X is the predictor (test) and Y is the criterion (performance).

X 21,30,27,26,25,26,25,31,32,15,28,25,15,27,24,26,24,31,25,19,33,18,25,20,19

Y 35,49,43,45,42,33,40,46,53,17,46,41,25,33,39,42,35,38,40,32,53,31,25,32,29

a. Compute the correlation

b. Compute the regression line (intercept and slope)

c. Compute the squared correlation.

d. Should she continue to use the test for the selection of employees? Explain. 15. A variable is normally distributed with a mean of 50 and a standard deviation of 36. Using this information evaluate the following probabilities: a. P(X > 55)= b. P(X< 43)= c. P(43