Math 151 , Fall'07, Wed. Sept. 12, Day 9 .After class. Hit Reload...

HW Day 9  Ch. 3 for Exam: Density curves, Normal: 68-95-99.7% rule  to Standardizing, p. 76.
To read for MONday:  We WILL use table A.   Moore doesn't separate out reading the z-table in the following; focus on just the z-table parts on first reading:  p. 76-80, Cum. proportion and  normal.  "Check" 3.22, 3. 23. "Backward" from prop. to z pp. 81-83.  Then  revisit and learn to deal with x's.We WILL use table A. 

Hand in NOTHING for Monday (Normal templates--you can count squares--may help!)
But I strongly encourage you to go through these problems, sketch and label and mark the normal curves.If you can, get the answers with the Applet. Leave room for computations.
----- Using table with "z"'s--standard normal.---------
Table use--z: Always sketch a normal curve first, mark the area you are looking for!  Do these with the Applet: Normal Density Curve on your CD or at   http://www.whfreeman.com/bps/, and check with your table answers.  (Uncheck the 2-tail box for most uses. Mean 0, s.d. 1) 
  p.80 3.10 z's to proportions, using Table A.
= = = = = = =
"Backward"--z :Always sketch a normal curve first, roughly mark the proportion=area you are given. 
p.83, 3.13 (backward z) Do with table, check using Applet: Normal Density Curve on your CD or at  http://bcs.whfreeman.com/bps4e.
p. 89, 3.52  Quartiles of normal dist.    Use the Applet and also, use table A to find the quartiles.  Your answers may differ in the second decimal place because the Applet only goes by .02's on the z-axis --.64, .66, .68... and Table A goes by .01's.

--
 = = = =  Using table with "x"'s--"raw" values. = = = =
 Begin these by drawing and labeling the appropriate normal curve for each question, leaving space for computation.  Normal templates-may help. Then use the Applet: Normal Density Curve on your CD or at   http://bcs.whfreeman.com/bps4e. to find the required values.  Write these on your paper.  Next, calculate the values using Table A.  Your answers from each method should be very close (the Table gives a bit more accuracy than the Applet.)
p. 87, 3.37 Jacob's score, and 3.39 top score. Mean, s.d. are before 3.32 on p. 86.
p. 87, 3.46 surprising difference in tails
 A. , What proportion of pregnancies last 310 days or more? Find Mean and s.d. in p.74, 3.7 (see below this box**) 
 p. 80-81 3.11 and 3.12 (locomotive adhesion, 2 dist's) 

..---(Separate page--probably won't finish Mon)--
-- "Backward Normal"-----------
Begin these by drawing and labeling the appropriate normal curve for each question, leaving space for computation.  Normal templates-may help. Then use the Applet: Normal Density Curve on your CD or at    http://bcs.whfreeman.com/bps4e. to find the required values.  Write these on your paper.  Next, calculate the values using Table A.  Your answers from each method should be very close (the Table gives a bit more accuracy than the Applet.)
p. 83, 3.14 IQ test
p. 87, 3.41 Abigail, top 20%.  Mean, s.d. are before 3.32 on p. 86.
p. 87, 3.42  quartiles  Mean, s.d. are before 3.32 on p. 86.

p. 179, 7.27 breaking bolts, (a, b +).  For (a), think carefully about which side of 90 you want: Does a bolt that breaks at 95 ksi qualify?  Does a bolt that breaks at 85 ksi qualify?   ALSO:  If they test every bolt and  throw away all bolts that break at 70 ksi or below, what proportion do they throw away?

 Read, to discuss  Optional (more practice) 
 



 


 
 

p. 86 3.30 z's to proportions
-------------------
  ..

"Backward" 
p. 86, 3.31 (backward z)
p. 89, 3.53
--------------------


Work through the  Normal Probability Practice handout.



 
**[In 1973] the following item appeared in Dear Abby's column:  
     Dear Abby: You wrote in your column that a woman is pregnant for 266 days. Who said so? I carried my baby for ten months  and five days, and there is no doubt about it because I know the exact date my baby was conceived. My husband is in the Navy  and it couldn't have possibly been conceived any other time because I saw him only once for an hour, and I didn't see him again  until the day before the baby was born. I don't drink or run around, and there is no way this baby isn't his, so please print a retraction about that 266-day carrying time because otherwise I am in a lot of trouble.
                                                                               San Diego Reader
Abby's answer was consoling and gracious but not very statistical:

     Dear Reader: The average gestation period is 266 days. Some babies come early. Others come late. Yours was late.

The question here is not whether the baby was late. That fact is already known. At issue is the credibility of the length of the delay. Ten months and five days is approximately 310 days, which means that the pregnancy exceeded the norm by 44 days. [How unusual is that?]

First hourly exam next class, Day 10, Friday Sept 14. Sample exam  handed out  solutions linked here, NOT #13! outside my door & on reserve.  Closed book, but bring one sheet of notes (anything you like) and a calculator.
Exam will cover thru Ch. 3, Densities, 68-95-99.7% rule and standardizing, only, .
  You may stay late, if you don't have another obligation.  You don't have to work in the classroom;  you just have to sign in and say where you'll go (in the building!), on the clipboard.  If you want more than an hour, and have obligations before and after--or other problems-- see or email me to make a plan TODAY!, please! 

You may be asked to read SPSS output, but not how to produce it.  You will need to calculate a standard deviation for 4 data items, and show your work. The sample exam is not a complete list of everything that could be asked, but gives a good sense of "flavor".   For instance, you might be asked to create a boxplot, not just read one, to read a timeplot, etc.

Clinic Schedule (current now) (Hit reload on the Clinic Schedule too) 
Helen:  M 2-5, Tu 7:30-9:30, W 2:30-4:30, Th 11-12
Matthew: Th 3:30-5:30, F 1-3
Others in the clinic are learning stats (Math 251) and are a little ahead of this class (Helpers)
More help?  I'm here till 3:45 today.  Matthew will be available to answer questions by phone 8:45-10 pm Thursday evening, at 315-529-8756. (his email connection is creaky)

Questions on HW?  Normal, using 68-95-99.7 rule, standardizing.  HWDay 8,   NotesDay 7
Questions on exam material??  Sample exam ,  solutions linked here, NOT #13! ( Not Table A)

Continue Monday with
Normal distribution.  
   Applet: Normal Density Curve   http://bcs.whfreeman.com/bps4e
Handouts:  Last time:  Normal Templates: you can count squares for approximate answers using these density curves.
 Today:     Normal Probability Practice :  Table use summarized, with examples and practice problems  

 All Normal table use notes are at Day 8.


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