I think they make it pretty clear what to do here.  Look at each 5-digit sequence on Table B and write down the largest number.  Do this 50 times, so you will have written down 50 numbers (you will probably have quite a few 8's and 9's).  For the stemplot, your stems will always be 0. All your 9's, for example, will be written as a stem of 0 and then write all your 9's as the leaves.  Similarly, all your 8's will be a stem of 0, with all the 8's as leaves, and so on (of course, your smallest leaves will be in the first row and your largest leaves (the 9's) will be in the last row).

 

 

Questions that give you μ and σ are undoubtedly dealing with bell curves.  Make sure you have studied my lesson on the Distribution of the Sample Mean (Lesson 7 in the new edition, Lesson 6 in older editions).  Always be very careful to note, are they asking you for the probability of one individual value (X)?, or are they asking you for the probability of the average or mean of n values (x-bar, the sample mean)?  If you are dealing with X, use the X standardizing formula.  If you are dealing with x-bar, use the x-bar standardizing formula.

 

Also, note that you can only do probabilities for X in these cases if you are specifically told that X is normally distributed.  Otherwise, there is no X-bell curve, and the probability is unknown.  However, thanks to the Central Limit Theorem, we can always assume there is an x-bar bell curve (the sample mean is normally distributed), as long as n is large.

 

How big a sample size n do you need to reduce σ(x-bar), the standard deviation of x-bar, down to a certain amount?  You can solve that by some algebra, but I suggest you just use trial and error.  Try n = 10, for example, and see if that works.  If not try n = 20 or something.  Play the Price is Right Clock Game.  Try higher n's, lower n's until you home in on the n that works.  With a calculator, I contend you can arrive at the correct answer quite quickly.  Those of you who feel comfortable with algebra are certainly welcome to solve the problem that way.

 

Note, in Question 4, parts (c) and (d), it appears you do not have enough info to solve the problem because they have not given you a value for μ, the population mean.  That is because the actual value is irrelevant.  If you ever come across a problem like this, pretend that μ = 0, and then be careful to draw a picture and shade the region they describe.  Proceed to compute your z-score, etc.  Try it again, but this time using μ = 10 and making the appropriate adjustments to your bell curve and shade the region.  You will discover you get the exact same z-score.  This works no matter what you use for μ.  That's why the easiest choice is μ = 0.

 

Again, be sure to look at my question 10 in my Binomial Distribution lesson to understand how to approach this question.

 

Question 7 uses the Sampling Distribution simulator at Rice Virtual Lab in Statistics.  Read Carefully.  They first have you play around with it using a Normal Distribution.  But, the actual questions they ask want you to use a "Skewed Distribution".  Note that, in the top left corner, you are given the mean and standard deviation of the population (μ and σ).  The various questions you are being asked are about the distribution of the sample mean.  Compare the answers for the mean and standard deviation of x-bar that the applet is giving you (next to the third histogram) with the theoretical values you expect if you computed the mean and standard deviation of x-bar using the formulas I give you in Lesson 7 of my book.  This applet is illustrating the same concepts I discuss in Figures 1 and 2 in Lesson 7.