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# Hot Stats Topics

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Hello professor,

I also need help with question number 45 from the mixed review from chapter 4. It starts like this "Your campus newspaper decides to run a raffle..."

Hi Professor,

I am reviewing the examples on Chapter 8 and got stuck on something.
---------------
Example 122: In a 2007 study of different popular diets, 77 people used a modified* version of the
Atkins Diet for one year. Their mean weight change was -10.34 lbs.
Assume that the population standard deviation for all such weight
changes is known to be 15.51 pounds. Use a significance level of
0.05 to test the claim that the mean weight change is equal to zero.
Does the diet seem to be effective? Does the mean weight change
seem substantial enough to justify the diet? What assumptions are
necessary for the test we just conducted to be valid?
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The claim is: m=0 but why is it the null hypothesis and not the alternative hypothesis? I assumed when we test a claim it's going to be the alternative hypothesis and the opposite would be the null.

If a person bought 1 share of Google stock within the last year, what is the probability that the stock on that day closed within \$50 of the mean for that year (round to two places)? (Hint: this means the probability of being between 50 below and 50 above the mean). I cannot figure out the formula for this.. please help:)
M=1131.530876
SD=64.81327423

Hi Professor!
I have a simple question, that I got stuck on, I have watched stats professor (the video) and I understand what I needed to do for Sect. 8.4 #30 but I don't understand why? to get the P-value I was under the impression you would subtract 0.50 minus the shaded area on the Z-table? but in that problem we added the amount to 0.50. why did we do that ?

Chapter 8 Hypothesis testing ..this is in my homework
Stolen Aircraft
Test the claim that the standard deviation of the number of aircraft stolen each year in the united states is less than 15 if sample of 12 years had a standard deviation of 13.6. Use α = 0.05

A bag contains 50 names in it. A professor plans to draw three names from the bag to win a free
graphing calculator. How many different sets of three winners can be drawn from the bag?

1. Test the claim that the standard deviation of the number of aircraft stolen each year in the US is less than 15 if a sample of 12 years had a standard deviation of 13.6. use @=0.05.

2. A film editor feels that the standard deviation for the number of minutes in a video is 3.4 minutes. A sample of 24 videos has a standard deviation of 4.2 minutes. At @=0.05,is the samples standard deviation different from what the editor hypothesized?