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A correlation is a statistical relationship between two variables. If we wanted to know if vaccines work, we might look at the correlation between the use of the vaccine and whether it results in prevention of the infection or disease [1]. In this question, you are to see if there is a correlation between having had the chicken pox and the number of chickenpox vaccine doses given (varicella).

Some notes on interpreting the answer. The `had_chickenpox_column` is either 1 (for yes) or 2 (for no), and the `num_chickenpox_vaccine_column` is the number of doses a child has been given of the varicella vaccine. A positive correlation (e.g., `corr > 0`) means that an increase in `had_chickenpox_column` (which means more no's) would also increase the values of `num_chickenpox_vaccine_column` (which means more doses of vaccine). If there is a negative correlation (e.g., `corr < 0`), it indicates that having had chickenpox is related to an increase in the number of vaccine doses.

Also, `pval` is the probability that we observe a correlation between `had_chickenpox_column` and `num_chickenpox_vaccine_column` which is greater than or equal to a particular value occurred by chance. A small `pval` means that the observed correlation is highly unlikely to occur by chance. In this case, `pval` should be very small (will end in e-18 indicating a very small number).

[1] This isn't really the full picture, since we are not looking at when the dose was given. It's possible that children had chickenpox and then their parents went to get them the vaccine. Does this dataset have the data we would need to investigate the timing of the dose?