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rmeanstandard-deviationbinomial-theorem

Mean and Standard Deviation of x>=5 of 10000 data points binomial(10, 1/4)

I have a data range of 10,000 points as per:

data = rbinom(10000, size=10, prob=1/4)

I need to find the mean and standard deviation of the data values >=5.

There are approx 766 values as per:

sum(data >=5)

sum (or any other approach I can think of) produces a TRUE/FALSE and cannot be used within a mean or sd calculation. How do I divide up the actual values?!

Solution

  • If you want to get all the values of data which are greater than or equal to 5, rather than just a logical vector telling you if the values of data are greater than or equal to 5, you need to do data[data >= 5].

    So we can do:

    data = rbinom(10000, size=10, prob=1/4)

mean(data[data >= 5])
#> [1] 5.298153

sd(data[data >= 5])
#> [1] 0.5567141