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Level IV

## 95% confidence intervals

Hi All,

l am trying to get a summary from a data table, l would like the mean of a variable l10t, the standard error, and 95% confidence interval. It all seemed fairly straight forward, but am having trouble with the 95% confidence intervals, have tried different ways to no avail, currently have

``````dt2<< Summary(
Group( :Sample ),
Mean( :dilution factor, :l10t ),
Freq( "None" ),
Weight( "None" ),
Output Table( "log10t" ),
Std Err( :l10t ),
Confidence Interval( :l10t, 0.95),

l am obviously doing something incorrectly, can anyone offer some advice.

Thanks Heaps

4 REPLIES 4
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Staff

## Re: 95% confidence intervals

You can accomplish something similar like this:

``````Names Default To Here( 1 );
dt = Open( "\$SAMPLE_DATA/Big Class.jmp" );
platform = dt << Oneway(
Y( :height ),
X( :sex ),
Means and Std Dev( 1 ),
Box Plots( 1 ),
Mean Diamonds( 1 ),
Mean Error Bars( 1 ),
Std Dev Lines( 1 ),
Connect Means( 1 ),
Points Jittered( 1 ),
Grand Mean( 0 )
);
Wait( 0 );
Report( platform )[Outline Box( "Oneway Analysis of height By sex" )][
Outline Box( "Means and Std Deviations" )][Table Box( 1 )] << Make Into Data Table;
Report( platform ) << Close Window;``````

Place your group variable in the X() role.

Highlighted
Level IV

## Re: 95% confidence intervals

Hi mzwald,

Thanks very much for your help and your suggestion, i tried this code

``````platform = dt2 << Oneway(
Y( :l10t ),
X( :fold dilution ),
Means and Std Dev( 1 ),
Box Plots( 1 ),
Mean Diamonds( 1 ),
Mean Error Bars( 1 ),
Std Dev Lines( 1 ),
Connect Means( 1 ),
Points Jittered( 1 ),
Grand Mean( 0 )
);
Wait( 0 );
Report( platform )[Outline Box( "Oneway Analysis of height By sex" )][
Outline Box( "Means and Std Deviations" )][Table Box( 1 )] << Make Into Data Table;
Report( platform ) << Close Window;``````

and received the following error message

``Cannot subscript Display Box in access or evaluation of 'Report(platform)[Outline Box("Oneway Analysis of height By sex")]' , Report( platform )[/*###*/Outline Box( "Oneway Analysis of height By sex" )]``

however, l am almost there as to what i want to achieve for my data table with this,

``````dt2<< Summary(
Group( :Sample ),
Mean( :dilution factor, :l10t ),
Freq( "None" ),
Weight( "None" ),
Output Table( "log10t" ),
Std Err( :l10t ),
Confidence Interval( :Name ("Mean(l10t)")),
);

Loq = Data Table( "log10t" );

Loq << New Column( "Back T'sform Mean", Numeric, Continuous, Formula( Round(10^:Name ("Mean(l10t)"),0)));

Loq << New Column( "Back T'sform Std error", Numeric, Continuous, Formula(10^:Name ("Std Err(l10t)"), Format( "fixed dec", 6, 0 ) ) );``````

giving me this,

so l am almost there, l was hoping the confidence intervals would be a single simple line of code.

Thanks

Mickyboy

Highlighted
Staff

## Re: 95% confidence intervals

Well it looks like Summary doesn't currently support CI's, but you can always make a formula for them yourself.
The formulas for a 95% confidence interval (assuming a normal distribution) would be:
Upper95CI = mean + 1.96*stdev
Lower95CI = mean - 1.96*stdev
You can generate those two columns from the fields returned by the Summary platform. Those formulas will get you pretty close to what you are looking for.

Highlighted
Level IV

## Re: 95% confidence intervals

Hi mzwald,

i have used the following and has worked a treat

``New Column( "Lower 95% CI", Numeric, Continuous, Formula ( Round(:Name ("Mean(l10t)") - (:Name("Std Err(l10t)") * t Quantile (0.975,23)), 4)));``

if i have used the following to create a variable

``````dt2<< Summary(
Group( :Sample ),
Mean( :dilution factor, :l10t ),
Freq( "None" ),
Weight( "None" ),
Output Table( "log10t" ),
Std Err( :l10t ),