Statistics questions

[Dofuss3000]

If you select a 170 people randomly from the population and the average IQ of the general population is 100 (Standard Deviation 15) and half of them (85) score at or above 142, what is the probability of this? Is it astronomical? Like one in trillions.

Take someone with an IQ of 100 on three professional tests in one year, what is the probability of them getting a 140, SD 15 on the fourth IQ test?

 

[bonkers325]

do your own homework or at least show that you've made some vague attempts at it

 

[Dofuss3000]

lol

I am not in a statistics class, I just have some honest questions and if you can't solve them then thats your problem. Don't respond with an EXTREMELY predictable response, either solve it or shove off.

 

[JohnCU]

Originally posted by: Dofuss3000
lol

I am not in a statistics class, I just have some honest questions and if you can't solve them then thats your problem. Don't respond with an EXTREMELY predictable response, either solve it or shove off.

shove off aye aye cap'n

 

[tailes151]

Yes, it would be an extremely small chance. The odds that 1 person picked from the sample scores at or above a 142 is approx .0026

 

[Random Variable]

Originally posted by: tailes151
Yes, it would be an extremely small chance. The odds that 1 person picked from the sample scores at or above a 142 is approx .0026

Are you assuming that the original population follows a normal distribution.

 

[tailes151]

Originally posted by: Random Variable

Originally posted by: tailes151
Yes, it would be an extremely small chance. The odds that 1 person picked from the sample scores at or above a 142 is approx .0026

Are you assuming that the original population follows a normal distribution.

Yes. As all the problems Ive ever dealt with that were concerned with IQ were always stated as such.

 

[blinky8225]

Essentially non-existent. The probability that someone one has an IQ >= 142 is 0.0026. So, if you took 170 people, you would expect to find 0.442 people with such an IQ. (I know that there is no such thing as 0.442 people.) Thus, 85 people people having such an IQ ends up being over 127 standard deviations from the mean, which pretty much means there is no chance of that happening.

As for your second question, are you assuming that each test is independent, because that's just not true if the same person is taking the test. If a person has an IQ of 100, they have an IQ of 100. They don't get lucky and score higher some day.