The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Professional Associations » nyshsmath

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: A2/Trig #29
Replies: 11   Last Post: Jul 29, 2011 12:51 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]

Posts: 12
Registered: 6/25/06
Re: A2/Trig #29
Posted: Jul 5, 2011 10:03 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply
att1.html (4.3 K)

The answer to the question can only be expressed as a probability that there will be 15 players over the age of 20. I didn't see the rubric, but the question should have read, what is the probability that there were 15 players over the age of twenty. Nice idea for a question but the Regent's should know better. I would also accept an answer that the question has no determined answer.

-----Original Message-----
To: nyshsmath <>
Sent: Fri, Jun 24, 2011 12:14 pm
Subject: Re: A2/Trig #29

It seems to me that the clue in this question is "normally distributed". This question is being asked from the theoretical ideal situation.

>>> "Glenn Clemens" <> 6/24/2011 9:22 AM >>>

Can someone with a statistics background help me out with question 29 (82 video game players, ages normally distributed with mean 17 and std d 3; were there 15 players over the age of 20?).

Yes, in an ideal normal distribution (which I don?t think you?ll see with 82 data points), 15.9% of the scores should be more than 1 sigma above the mean. But in a sample from a normal, doesn?t this become an expected value? In the given problem, we would EXPECT about 13 players to be 20 years or older, but there could be more or there could be fewer.

Assume the 82 players were randomly sampled from a larger population whose ages are normally distributed with the given mean and std d. If I use a binomial distribution with n = 82 and p = 0.159, I get a 9.6% chance that there will be exactly 15 players over the age of 20 and a 32% chance that there will be 15 or more players over the age of 20. What then is the appropriate answer to ?Determine if there were 15 players in this study over the age of 20.?? Probably not but we can?t be even close to sure.

I do not like the wording of this question. But my probability and statistics education is a loooong time in the past. I?d appreciate a second (third, fourth, . . . dozenth) opinion.

Glenn Clemens

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.