Ascore that is 6 points below the mean corresponds to a z-score of z –0.50. what is the population standard deviation?

The minus sign of the z-score shows that the score is below the mean. 6 points below the mean means the difference of the score and mean is -6 z = (X-Mean)/SD -0.50 = -6 / SD SD = -6/-0.50 = 12 The population standard deviation = 12

Well if you have 20 bats you probably want 20 balls? you don’t have enough context to answer the question.