10-04-2007, 08:22 PM
Ok, first things first. Be sure to write down on your scrap paper the information given to you at the beginning of the exam. You are given various significance levels and the appropriate Z score. They write it in an unusual way. It is written as follows:
Z. 0.0050 1.96
Z 0.010 1.645
You need this data to answer four or five questions in which you are asked about significance levels but not given the critical z-score. Thatâs why you need this information.
There were no questions, on my exam, that required you to calculate the correlation coefficient ( r ). There were two questions of this type: What can you say about the relationship of x and y if r = -0.80. Answer: strong and negative, although the answer on the exam used the word inverse, not negative. There was also a question that asked for the formula of the correlation coefficient of non-determination. I believe that was 1-r^2. There was also a question that asked what the correlation coefficient of determination tells you?
There were a few questions on the regression line. Again, no questions asked me to calculate the slope or y-intercept. I had questions that asked about the line. Given y = a + bx. What is b? Answer: the slope. What is a? Answer: the y-intercept. Then there were two questions, I believe, in which they gave you a value for x and asked you to solve for y. Very simple stuff there.
There were a few questions on hypothesis testing. I believe there were two questions that laid out a scenario then asked you to select the appropriate null and alternative hypothesis. There were one or two questions on p-values. Specifically, given the p-value of 0.034 and a significance level of 0.05, what would you say about the hypothesis. Your answers were to reject, do not reject and two off the wall answers. The answer is reject since the p-value is less than the significance level.
There were a few probability questions. One question was the following: You have 3 red balls, 2 yellow balls and 5 green balls. You select one ball, write down the color, and then place the ball back in the group. If you repeat this procedure 1000 times, how many red balls would you expect to draw? Answer: 300. Since there are 10 balls in total and 3 are red, you would have 3 in 10 chance of drawing the red ball. So, if the experiment is repeated 1000 times you would expect 300 red balls to be drawn. Another probability question was: Maria goes to Cafà A 60 percent of the time and Cafà B 40 percent of the time. Regardless of which Cafà she goes to, she orders the cafà moca 50 percent of the time. What is the probability that Maria will go to Cafà A and order the cafà moca? Answer: Since this an intersection of events and they are independent of one another, we use the multiplication rule. So we multiply Cafà A probability, 0.6, by the probability of ordering the cafà moca, which is 0.5. Answer is 30 percent or 0.3. The next probability problem was: Voter A votes 45 percent of the time, Voter B votes 30 percent of the time and Voter A and Voter B vote together 20 percent of the time. What is the probability that Voter A or Voter B will vote? Answer: You use the addition rule for non-mutually exclusive events. So, 45 percent + 30 percent â 20 percent = 55 percent.
The final part of the exam was easy. There were questions that related to the normal distribution so you need to know that 1 standard deviation = 68%, 2 standard deviations = 95% and 3 standard deviations = 99.7%. There was a question that said: the population mean for the height of women is 60 inches with a standard deviation of 2.5 inches. What percentage of women will be between 57.5 and 62.5 inches? Since this is 1 standard deviation below and above the mean, the answer is 68%. Then they ask the same question but ask, what is the percentage of women between 57.5 and 60 inches? Since this is one standard deviation below the mean, but not above the mean you would take half of the 1 standard deviation amount. Thus, the answer is 34%. Another question gives you a mean of 100, standard deviation of 0.5. What is the range of values when looking to contain 95% of the population? Remember, 95% is 2 standard deviations so the answer is 99-101.
Just buy Idiotâs Guide to Statistics and study it thoroughly and you will do fine on this exam. Take the time you need to study, and you will be just fine.
Z. 0.0050 1.96
Z 0.010 1.645
You need this data to answer four or five questions in which you are asked about significance levels but not given the critical z-score. Thatâs why you need this information.
There were no questions, on my exam, that required you to calculate the correlation coefficient ( r ). There were two questions of this type: What can you say about the relationship of x and y if r = -0.80. Answer: strong and negative, although the answer on the exam used the word inverse, not negative. There was also a question that asked for the formula of the correlation coefficient of non-determination. I believe that was 1-r^2. There was also a question that asked what the correlation coefficient of determination tells you?
There were a few questions on the regression line. Again, no questions asked me to calculate the slope or y-intercept. I had questions that asked about the line. Given y = a + bx. What is b? Answer: the slope. What is a? Answer: the y-intercept. Then there were two questions, I believe, in which they gave you a value for x and asked you to solve for y. Very simple stuff there.
There were a few questions on hypothesis testing. I believe there were two questions that laid out a scenario then asked you to select the appropriate null and alternative hypothesis. There were one or two questions on p-values. Specifically, given the p-value of 0.034 and a significance level of 0.05, what would you say about the hypothesis. Your answers were to reject, do not reject and two off the wall answers. The answer is reject since the p-value is less than the significance level.
There were a few probability questions. One question was the following: You have 3 red balls, 2 yellow balls and 5 green balls. You select one ball, write down the color, and then place the ball back in the group. If you repeat this procedure 1000 times, how many red balls would you expect to draw? Answer: 300. Since there are 10 balls in total and 3 are red, you would have 3 in 10 chance of drawing the red ball. So, if the experiment is repeated 1000 times you would expect 300 red balls to be drawn. Another probability question was: Maria goes to Cafà A 60 percent of the time and Cafà B 40 percent of the time. Regardless of which Cafà she goes to, she orders the cafà moca 50 percent of the time. What is the probability that Maria will go to Cafà A and order the cafà moca? Answer: Since this an intersection of events and they are independent of one another, we use the multiplication rule. So we multiply Cafà A probability, 0.6, by the probability of ordering the cafà moca, which is 0.5. Answer is 30 percent or 0.3. The next probability problem was: Voter A votes 45 percent of the time, Voter B votes 30 percent of the time and Voter A and Voter B vote together 20 percent of the time. What is the probability that Voter A or Voter B will vote? Answer: You use the addition rule for non-mutually exclusive events. So, 45 percent + 30 percent â 20 percent = 55 percent.
The final part of the exam was easy. There were questions that related to the normal distribution so you need to know that 1 standard deviation = 68%, 2 standard deviations = 95% and 3 standard deviations = 99.7%. There was a question that said: the population mean for the height of women is 60 inches with a standard deviation of 2.5 inches. What percentage of women will be between 57.5 and 62.5 inches? Since this is 1 standard deviation below and above the mean, the answer is 68%. Then they ask the same question but ask, what is the percentage of women between 57.5 and 60 inches? Since this is one standard deviation below the mean, but not above the mean you would take half of the 1 standard deviation amount. Thus, the answer is 34%. Another question gives you a mean of 100, standard deviation of 0.5. What is the range of values when looking to contain 95% of the population? Remember, 95% is 2 standard deviations so the answer is 99-101.
Just buy Idiotâs Guide to Statistics and study it thoroughly and you will do fine on this exam. Take the time you need to study, and you will be just fine.
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