Stat 1000: ICYMI Tips for Assignment 3

Published: Sat, 02/21/15

Did you read my tips on how to study and learn Stat 1000?  If not, here is a link to those important suggestions:
Did you read my Calculator Tips?  If not, here is a link to those important suggestions:
Did you see my tips for Assignment 1? Click here.
Did you see my tips for Assignment 2? Click here.
Tips for Assignment 2

Study Lessons 4 and 5 in my study book (if you have it) to learn the concepts involved in Assignment 3.  Don't start working on the assignment too soon.  Study and learn the lesson first, and use the assignment to test your knowledge.  Of course, always seek out assistance from my book, your course notes, etc. if you ever hit a question you don't understand, but try not to be learning things as you do an assignment.  Learn first, then put your learning to the test.


Exception: Always do any JMP stuff open-book.  Have my tips in front of you, and let me guide you step-by-step through any JMP stuff.  JMP is just "busy" work.  The sooner you get it done and can move on to productive things like understanding the concepts and interpreting the JMP outputs, the better off you will be.
Don't have my book or audio lectures?  You can download a free sample of my book and audio lectures containing Lesson 1:
A Warning about StatsPortal
Make sure that you are using Firefox for your browser.  Don't even use Internet Explorer.  It actually also has some glitches in the HTML editor boxes.

Do note that every time you exit a question in StatsPortal, the next time you return to it, the data may very well change.  Do not press the "back-up" button on your browser in a question.  That, too, will change the data.  When you are prepared to actually do a question, open the link, keep it open, and do not close it until you have submitted your answers.  Be sure to press "Save Answers" once you have done any calculations and entered any information to ensure the data does not change and force you to start over again.

After you submit the answer to a question, if you have been marked wrong on any parts, be sure that you write down the correct answers before you exit the screen (or grab a screen shot).  To try a second attempt at the question do not click the link to the question again, that will change the data and you will have to start all over again.  Also, DO NOT click "try again" or make a "second attempt."  That will also reset the data.

Instead, exit back to the home screen where they show the links for all the different questions on the assignment.  Where it shows the tries for a question on the right side of your screen, you should see the "1" grayed out, showing that you have had 1 attempt.  Click the number "2" to get your second attempt with the same data.  That way you can enter the answers you already know are correct and focus on correcting your mistakes.

You should also have already downloaded the JMP statistical software which was provided with either one of the course options for StatsPortal as mentioned in your course outline.

Make sure you have gone through Assignment 0 completely to learn how to use the interface.  I also suggest you print out a copy of question 8 in Assignment 0 (Long Answer Questions - Part 3) so that you have the steps for saving and uploading files into the HTML editor in front of you.
Question 1: Uniform
This question is very similar to my question 2 in Lesson 4.

In part (d) you will have to work backwards.  Arbitrarily mark b as some random value on your horizontal axis.  Then mark the given right endpoint further along on the right axis.  Shade the region between b and the given right endpoint.  That rectangular shaded area is what they are describing.  You are given the proportion which tells you the area of the shaded region.  You also know the height of the shaded region (your answer from part (a)).  So, you can establish what the width of the shaded region must be because you know the width times the height equals the area.  Then, you can establish what b must be knowing that Right - Left gives you the width.

For part (e), there is a really easy way to figure out the interquartile range if you think about it.  After all, that is the width of the middle 50%.
Question 2: Forward z
I strongly recommend you read my section in Lesson 4 about the Z Bell Curve Ladder and the X Bell Curve Ladder and make the ladder every single time you have a bell curve problem.  Then climb up or down the rungs.  Many students are guilty of not thinking a problem through, and consequently looking at Table A too soon.  The ladder trains you to focus on the fact that Table A deals with z scores and Left Areas, but your problem may be interested in something else.

You will be using Table A for much of this assignment.  Here is a link where you can download the table if you have not already done so:

This is very similar to my Lesson 4, question 5.  Make sure you have done all of those questions first and have confirmed by repeated attempts, that you can get them 100% correct every time before you attempt this question on the assignment.

IT IS IMPERATIVE THAT A STUDENT CAN CONSISTENTLY GET MY QUESTIONS 5 AND 6 CORRECT EVERY TIME WITHOUT EXCEPTION.  BE HARD ON YOURSELF.  Students who make mistakes on this stuff, and find themselves saying things like, "Oh, I forgot to subtract from 1; or, oh, I didn't realize that was the right area," are just setting themselves up to get most of the exam questions wrong.  Always use my bell curve ladders to help you focus on the problem and always draw a diagram to visualize the problem.
Question 3: Backward z
This is very similar to my Lesson 4, question 6.  Make sure you have done all of those questions first and have confirmed by repeated attempts, that you can get them 100% correct every time before you attempt this question on the assignment. 

IT IS IMPERATIVE THAT A STUDENT CAN CONSISTENTLY GET MY QUESTIONS 5 AND 6 CORRECT EVERY TIME WITHOUT EXCEPTION.  BE HARD ON YOURSELF.  Students who make mistakes on this stuff, and find themselves saying things like, "Oh, I forgot to subtract from 1; or, oh, I didn't realize that was the right area," are just setting themselves up to get most of the exam questions wrong.  Always use my bell curve ladders to help you focus on the problem and always draw a diagram to visualize the problem.

For part (a), note that I also do a percentile example in my question 7.  As I say in my question 7, the 80th percentile, for example, is the z-score that has 80% of the area to the left of that score.

In part (d), do note that it is b they want, not -b, so be sure to determine the value of the z-score on the right side of the region.
Question 4: Normal
Make sure you have studied all my X-Bell Curve problems (questions 9 to the end) in Lesson 4 before you attempt this question.  Make sure you use the X-Bell Curve Ladder to help you work your way through each part of this question.

You also need to know the 68-95-99.7 Rule taught earlier in my lesson (questions 3 and 4 in Lesson 4).  But, only use this rule to solve part (e).  Never use the 68-95-99.7 rule unless you are clearly told to do so!

Part (h) is all about z scores.  The higher your z score in a normal distribution, the better you did relative to others.  See my question 14 in Lesson 4 for an example of this principle.
Question 5: Probability
This is a question best solved by Venn Diagrams.  Make sure you have studied that section in Lesson 5 of my book and have done questions 14 to 18 before you attempt this question.  Make sure you have definitely looked over my examples of how to prove two events are independent or not in those questions (as well as others earlier in the lesson). 

This question is quite similar to my question 18.
Question 6: Probability Distribution
This question is a good example of a 2-way table problem.  It is sort of a combination of my Lesson 5, questions 4, 5 and 6.

For questions 1 and 2:
Don't forget to click the Html Editor link before you type your answers into their box.

I show you how to determine a Sample Space through the use of two-way tables if necessary in Lesson 6 of my book.  Note that all you are asked for is the sample space in each part, so your answer would be something like this (don't forget to use those squiggly brackets "{}").For example, here is the sample space for the outcome of flipping a coin twice where H=heads and T=tails:  {HH, HT, TH, HH}.

Don't state the probabilities!  You are not asked for the probabilities.  In fact, in many of the situations students will be given for this problem, it is impossible to know the probabilities.  You are just asked for the sample space.

Focus on what you are asked to select.  Is it just the colour of the candy you are interested in (Purple, Yellow or Red?, P, Y or R). Is it the flavour of the candies?

For question 3:
Now, you are asked to compute probabilities.  You can use the actual counts of each candy and the sample spaces you found in the previous two questions to help here.

In 3 part (e), you are asked for first is lemon OR second is cherry.  NOT AND!

I think it is a good idea to use my "check-mark method" that I show you in my Venn diagrams section when dealing with AND or OR.  In your sample space, check off all the outcomes that belong to A.  Now go back and check off all the outcomes that belong to B.  This might mean you are checking off the same outcome twice.
  • If you want A and B, add up all the probabilities that have been checked off twice.  (Those are the outcomes that belong to both A and B, as required.)
  • If you want A or B, add up any probability that has at least one check mark.  (Those are the outcomes that belong to at least one of A or B, as required.)