Exercise

# Standard error

Previously we observed how to calculate the standard deviation using the `.std()`

method. In this exercise, you will explore how to calculate standard deviation for a conversion rate, which requires a slightly different procedure. You will calculate this step by step in this exercise.

Loaded for you is our inner merged dataset `purchase_data`

as well as the computed `conversion_rate`

value.

Instructions

**100 XP**

- Find the number of paywall views in the dataset using
`.count()`

. Store this in`n`

. - Calculate a quantity we will call
`v`

by finding the`conversion_rate`

times the rate of**not**converting. - Now find our variance,
`var`

, by dividing`v`

by`n`

. This is the variance of our conversion rate estimate. - Finally the square root of
`var`

has been taken and stored as the variable`se`

for you. This is the standard error of our estimate.