FAQ: A/B Testing: Sample Size Calculators - Review

This community-built FAQ covers the “Review” exercise from the lesson “A/B Testing: Sample Size Calculators”.

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This exercise can be found in the following Codecademy content:

Master Statistics with Python

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Hi,

The min sample size is for 2 variants?

My best,
David Dias

Hello,
This topic is not clear to me. It says to check the solution, to check how it works. However, this number is not explained how to be calculated:

# calculate total sample size: 
samp_size= 	2060
print("sample size: ", samp_size)

A topic where it encourages keeping in mind the sample size, calculates beforehand and not to interfere with the test without explaining how to calculate it. It’s really poor, keeping in mind the previous module lacks the simplicity in the examples provided and/or additional resources to reinforce its content.

I am also confused how the sample size is equal to 2060 - my code is identical to the solution, but the calculator does not show 2060, it is showing me 180000 instead.

I was hoping to be taught the function that the “sample size calculator” is using. What is the point of driving home that we need to calculate sample sizes in advance but not giving us the mathmatical tools to do so. Or are we just ment to bookmark the generator?

Saying that, I guess the function is here in the html code:
function getSampleSize(minimum_detectable, significance, conversion_rate) {
let zscore = 1.959964
if(significance == 0.15) {
zscore = 1.439531
}
else if(significance == 0.1){
zscore = 1.644854
}

let factor = 2*(0.8416212+zscore)**2
let conv_b = conversion_rate * (1+minimum_detectable)

let numerator = Math.sqrt(conversion_rate * (1 - conversion_rate) + conv_b * (1-conv_b));
let denominator = Math.abs(conversion_rate * minimum_detectable);
let min_sample_size = factor * Math.pow(numerator/denominator, 2);

return parseFloat(min_sample_size.toPrecision(3));