how to calculate 99% confidence interval in matlab

To calculate the 99% confidence interval for a sample in Matlab, you can use the tinv function from the statistics toolbox. The formula to calculate the confidence interval is:

main.m
CI = sampleMean +/- tinv(alpha/2, n-1) * SEM
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where:

• sampleMean: the mean of the sample
• alpha: significance level (here, 0.01 for 99% confidence interval)
• n: sample size
• SEM: the standard error of the mean, calculated as std(sample)/sqrt(n)

Here's an example code snippet:

main.m
% generate a random sample of size 30
sample = randn(30,1);

% calculate sample mean and SEM
sampleMean = mean(sample);
n = length(sample);
SEM = std(sample)/sqrt(n);

% calculate t-value for alpha=0.01 and n-1 degrees of freedom
alpha = 0.01;
t = tinv(alpha/2, n-1);

% calculate confidence interval bounds
CI_lower = sampleMean - t*SEM;
CI_upper = sampleMean + t*SEM;
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In this example, CI_lower and CI_upper represent the lower and upper bounds of the 99% confidence interval.