# finding the shape,sd and mean

• Jul 14th 2008, 04:55 AM
lunaj
finding the shape,sd and mean
im having trouble finding (basically everything) i cant seem to figure out the problem with the given numbers.

In the problem it says that 39% of housholds have a dog in your city and that you takes a simple random sample of 50 households.

basically wer have to describe the shape, mean, and standard deviation.

i assume the .39 is the population mean and 50 is the sample observtion. i could be all wrong though. help please!
• Jul 14th 2008, 05:00 AM
CaptainBlack
Quote:

Originally Posted by lunaj
im having trouble finding (basically everything) i cant seem to figure out the problem with the given numbers.

In the problem it says that 39% of housholds have a dog in your city and that you takes a simple random sample of 50 households.

basically wer have to describe the shape, mean, and standard deviation.

i assume the .39 is the population mean and 50 is the sample observtion. i could be all wrong though. help please!

The number of a of households with a dog in a sample of $\displaystyle 50$ has a binomial distribution $\displaystyle B(50,0.39)$ , which we know has mean $\displaystyle 0.39 \times 50=18.5$, and a standard deviation of $\displaystyle \sqrt{50 \times 0.39 \times (1-0.39)}$

RonL
• Jul 14th 2008, 05:17 AM
lunaj
thank you so much!

im taking the course online so it keeps getting harder and harder. i dont think we've gone over the binomial thing or how to find a mean the way you did. so far its been given to us or there are multiple numbers and we find the mean.