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Thursday, April 06, 2006 


Chello, Chello, Chello
Yes i am today's scribe and ummm i'm not sure how to put pictures on this thingy cause i'm not a big computer freak well i mean i just dont like drawing and i just dont kno how lol:) SRY
So when i put "DIAGRAM" threres prolly a diagram of a 95% confidence interval ok kool, here we go.

Today we started off with some morning announcements and then Mr.K told some jokes, one was really good that i thought was true and then the others were all right and yeah thats wat we did to start off our day :) Oh today was a single class day!

We also did some dictionary notes and here they are:

Constructing Confidence Intervals

Step 1: Decide on the desired degree of confidence
Example: 95%

Step 2: Determine, with the aid of a diagram, the area in the trials of the normal curve.
Example: A Diagram of a 95% Confidence Interval Goes here Sorry:)

Step 3: Using tables or InvNorm(area) on your calculator find the values of Z-score low and Z-score high.
Example: InvNorm(0.025) = -1.96
Z-score low=-1.96 Z-score high=1.96

Step 4: Use the values Z-score low and Z-score high to construct your confidence interval as follows: (Meu-Z score X standard deviation, Meu+Z score X standard deviation)
Example: The 95% confidence interval for a normal distribution with M=63 and Standard Deviation=8 is: (63-(1.96)(8),63+(1.96)(8)) OR (47.32,78.68)

Percent Margin of Error

For the normal approximation of any binomial distribution we find the percent margin of error as follows: % margin of error= Z score(Standard deviation)/ n X 100

Z score is the appropriate Z score to generate a given confidence interval.
Standard Deviation symbol is the standard deviation symbol
n is the total number of trials in a given binomial experiment
Example: Given the bove data taken from a binomial experiment that was done 50 times(n=50)
% margin of error= (1.96)(8) / 50 X 100% = 31.36%

Theres your dictionary notes for the day and sorry for my illeteracy for symbols and suff lol please forgive:)

Now today we looked at a table of Z scores in our book on page 355, that table we must know how to use because it will be given to us on our exam at the end of the year during the time when we cannot use our calculators.

Today we also did a little question on the board that involved constructing a 95% confidence interval and finding the % margin of error for the amount of people wearing jeans in a mall out of 340 people so here it is:

n=340 p=238/340 = .70
M=np=238 (M-1.96(8.45),M+1.96(8.45))
nq=102 (238-1.96(8.45),238+1.96(8.45))

Standard deviation=the square root of npq
=square root of 340(.70)(.30)
= 8.45

% margin of error= (1.96)(8.45) / 340 X 100 = 4.87%

All of this means that if you repeat this experiment we are 95% confident that19 times out of 20 the data will fall between 221 and 255, so we will get an answer that is = to 238+/- 4.87%

We also have homework on PAGE 145 # 1-3, and we have a pre-test tomorrow so be sure to STUDY and dont forget k :)

Well that rap's it up for my scribe hope u can understand it lol but yeah have a good day and stuff BUH BYE THANK U

p.s tomorrows scribe will be NIK #1/2 :)

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