A simple random sample is collected to understand the Australians' opinion on shared bikes. 50 responses are "yes" to the question "would you like to use a share bike at a small cost (10 cents per km)?" and the remaining 22 answers are "no". A venture capital (VC) understands that investing in the shared bike project would be profitable if and only if the population proportion of the "yes" answer to the survey question is higher than 0.7.

What is the standard deviation of this sample?