Question

The birth weights for twins are normally distributed with a mean of 2353 grams and a standard deviation of 647 grams. use z-scores to determine which birth weight could be considered unusual.

Answer 1

Z-scores allow us to determine how far from the mean value is the data point given. It is usually considered an "unusual value" if the data has a z-score of that has an absolute value greater than 2. Z-scores are calculated through the following equation,
                           z-score = (data point - mean) / standard deviation