3. A large group of students took a test in English and the final grades have a mean of 75 and a standard deviation of 8. If we can approximate the distribution of these grades by a normal distribution. What percentage of the students
(i) Scored higher than 70?
(ii) Should pass the test(grades 2 >= 60)
(iii) Should fail the test(grades <60?
4. An industrial designer wants to determine the average amount of time it takes an adult to assemble an"easy to assemble" toy. A sample of 56 times yielded an average time of 20,5 minutes, with a sample standard deviation of 6.25 minutes.
(iii)Find the 95% confidence interval for the mean assembly time.
(iv)Find the 99% confidence interval for the mean assembly time.
5. 450 workers were selected at random from a district. Their mean income was $. I 40 per month. With standard deviation of $. 14.5. Do you believe that the average income of the workers community in the district is $ 135?
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Brent@GMATPrepNow
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These are not GMT-style questions.mim wrote:3. A large group of students took a test in English and the final grades have a mean of 75 and a standard deviation of 8. If we can approximate the distribution of these grades by a normal distribution. What percentage of the students
(i) Scored higher than 70?
(ii) Should pass the test(grades 2 >= 60)
(iii) Should fail the test(grades <60?
4. An industrial designer wants to determine the average amount of time it takes an adult to assemble an"easy to assemble" toy. A sample of 56 times yielded an average time of 20,5 minutes, with a sample standard deviation of 6.25 minutes.
(iii)Find the 95% confidence interval for the mean assembly time.
(iv)Find the 99% confidence interval for the mean assembly time.
5. 450 workers were selected at random from a district. Their mean income was $. I 40 per month. With standard deviation of $. 14.5. Do you believe that the average income of the workers community in the district is $ 135?
To begin, some require knowledge of Normal Distributions which are NOT tested on the GMAT.
The last question is particularly awful (Do you believe that the average income of the workers community in the district is $ 135?) Is this a YES/NO question based on one's BELIEF?
What's the source of these gems?
I wrote an article about spotting sub-standard GMAT questions - https://www.gmatprepnow.com/articles/questions-questions
Cheers,
Brent
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Agree with Brent. Stay away from random question banks. You need to get accustomed to the style of GMAT questions. It is better for you to rework questions you have done than scour the ends of the Internet for bad GMAT questions.
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This looks like a Stats 101 homework assignment to me, guys 
Can't blame the OP for wanting to get great BTG-style explanations, though!
OP, these are all fairly standard stats questions: for the first one, you want to find the z-scores that correspond to 60 and 70; for the second, just do this, and for the third, is their income 40¢ a month or 40$ (I can't tell from the formatting)?
Can't blame the OP for wanting to get great BTG-style explanations, though!
OP, these are all fairly standard stats questions: for the first one, you want to find the z-scores that correspond to 60 and 70; for the second, just do this, and for the third, is their income 40¢ a month or 40$ (I can't tell from the formatting)?
