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Topic: Re: t-table confidence intervals
Replies: 0

 Pat Ballew Posts: 356 Registered: 12/3/04
Re: t-table confidence intervals
Posted: Feb 13, 1997 12:28 PM

After sending a post this morning and saying that I thought there was
a way to do t-tests for common levels I felt bad that I had not done
that yet for my kids. I kept telling myself that part of the reason
was that I wanted to be sure that they understood by making them
construct the process by hand.. but even I had to admit it was partly
because I was too lazy.... So, in atonement I have written a program
that will do a confidence interval for samples up to 30, and (I hope)
do proportions for any sample size. Beyond N=30 the critical values
are the Z-values (1.96 for 95% etc)
You must also load the program "tval" as this loads the critical
values in the List spaces and is called from inside the program.
I have attached a file that can be downloaded directly to your
Graph-link software , and copied below the text form of the programs
for those who do NOT have link software...
If this has flaws, let me know as I gave it to my class only a few
minutes ago, it has NOT been tested yet.

Hope this is of some value, at least as a starter to get people
sending some better programs for all the things the ti-82 will not do.

I also have a couple of small programs that list Binomial and Cum
Binomial prob up to the limit of the Lists if these are of interest to
anyone.
Pat Ballew
MIsawa, Japan

I tried to clear up the glitches that come up when programs are
converted to text... sorry if I missed any,,, If it can't be corrected

Pat

This is the program I called "CONFINT.82P"
:ClrHome
:prgmTVAL
:Lbl J
:Disp "ENTER MEAN"
:Input M
:Disp "ENTER STDEV"
:Input S
:Disp "ENTER SAMPLE SIZE"
:Input N
:ClrHome
:S/sqrt(n)->E
:Goto Q
:Lbl K
:Disp "ENTER P"
:Input P
:Disp "ENTER SAMPLE SIZE"
:Input N
:ClrHome
:N*P->M
:sqrt(P*(1-P)/(N))->E
:32->N
:Lbl Q
:If N->30
:32->N
PERCENT",D,"99 PERCENT",E,"QUIT",F)
:Lbl A
:M+L1(N-1)*E -> H
:M-L1(N-1)*E -> L
:Goto G
:Lbl B
:M+L2(N-1)* -> H
:M-L2(N-1)*E -> L
:Goto G
:Lbl C
:M+L3(N-1)*E -> H
:M-L3(N-1)*E -> L
:Goto G
:Lbl D
:M+L4(N-1)*E -> H
:M-L4(N-1)*E -> L
:Goto G
:Lbl E
:M+L5(N-1)*E -> H
:M-L5(N-1)*E -> L
:Lbl G
:ClrHome
:Output(2,1,L)
:Output(3,2,"<=X<=")
:Output(4,3,H)
:Output(6,1,"ENTER TO CONT")
:Pause
:Goto Q
:Lbl F
:Stop

AND THIS IS THE "TVAL' PROGRAM WHICH STORES THE T-CRITICAL VALUES FOR
EACH DF... IF ANY OF THESE WERE MISTYPED, THEY CAN BE CORRECTED AS I
DID *NOT* LOCK THE FILES... BUT THEY SHOULD BE LOCKED WHEN GIVEN TO
THE KIDS TO AVOID HAVING THEM EDITED...

:
:ClrList L1,L2,L3,L4,L5
:{3.078,1.886,1.638,1.533,1.476,1.440,1.415,1.397,1.383,1.372,1.363,1.
356,1.350,1.345,1.341,1.337,1.333,1.330,1.328,1.325,1.323,1.321,1.319,
1.318,1.316,1.315,1.314,1.313,1.311,1.310,1.282}->L1
:{6.314,2.920,2.353,2.132,2.015,1.943,1.895,1.860,1.833,1.812,1.796,1.
782,1.771,1.761,1.753,1.746,1.740,1.734,1.729,1.725,1.721,1.717,1.714,
1.711,1.708,1.706,1.703,1.701,1.699,1.697,1.645}-> L2
:{12.706,4.302,3.182,2.776,2.571,2.447,2.365,2.306,2.262,2.228,2.201,2
.179,2.160,2.145,2.131,2.120,2.11,2.101,2.093,2.086,2.080,2.074,2.069,
2.064,2.060,2.056,2.052,2.048,2.045,2.042,1.960}->L3
:{31.820,6.964,4.54,3.747,3.365,3.143,2.998,2.896,2.821,2.764,2.718,2.
681,2.650,2.624,2.602,2.583,2.567,2.552,2.539,2.528,2.517,2.508,2.5,2.
492,2.485,2.478,2.473,2.467,2.462,2.457,2.326}->L4
:{63.605,9.92,5.84,4.604,4.031,3.707,3.499,3.355,3.25,3.169,3.106,3.05
5,3.012,2.977,2.947,2.92,2.898,2.878,2.861,2.845,2.831,2.818,2.807,2.7
97,2.787,2.779,2.77,2.763,2.756,2.75,2.576}-> L5

The following is an attached File item from cc:Mail. It contains
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through various mail systems. To decode the file use the UUDECODE
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--------------------------------- Cut Here ---------------------------------

The following is an attached File item from cc:Mail. It contains
information that had to be encoded to ensure successful transmission
through various mail systems. To decode the file use the UUDECODE
program.
--------------------------------- Cut Here ---------------------------------