# Recent content by devimon

1. ### Comparing means with known standard deviation known

1). The average number of pages for a simple random sample of 20 physics textbooks is 435. The average number of pages for a simple random sample of 25 mathematics textbooks is 404. Assume that all page length for each types of textbooks is normally distributed. The standard deviation of page...
2. ### Confidence intervals, proportions

A simple random sample of 1000 New Yorkers finds that 87 are left-handed. (a) Find the 95% confidence interval for the proportion of New Yorkers who are left-handed. The answer my professor gave and the answer that I got are completely off from each other. Here is what I have so far n = 1000...
3. ### Normal Approximation questions. Finding p?

1) An ESP test involves five shapes (star, square, circle, wave, cross) on cards. We record 1000 attempts. (a) What is the probability that a subject without ESP will be successful in at least 24% of the attempts?(b) The researcher considers evidence of ESP to a proportion of successes so large...
4. ### Normal Approximation probability question

Consider a four-sided die loaded so that 1 shows 40% of the time. If we roll this die 50,1000,2000,4000,8000 times, find the probability in each case that at least 42% of the rolls are 1's Can you please help me understand how to calculate the italicized part of the answer? Answer: P =...
5. ### Normal Approximation question

1) A fair coin is tossed 600 times. What is the probability that the number of heads will be between 290 and 310? (I have the answer, but I need help with the calculations of certain parts of the answer) Answer: p = 0.5, n = 600 ---------> I don't know how to calculate p mean...