Do some books categories receive on average better ratings than others?

Do fantasy books on average get better ratings than sci-fi books? The answer seems to be yes, according to this little data science project I’ve build from Goodreads data.

In this project I’ve grouped all titles in the data set by category, and then calculated the mean and standard deviation for each one of them. Then I’ve followed this good tutorial to compute the confidence interval for each category, and finally I’ve plotted mean and confidence interval (with 99% confidence) in a chart, ...