The mean of a set of normally distributed data is 600 with a standard devastation of 20. what percent of data is between 580 and 620

Rachel is studying the population of a particular bird species in a national park. she observes every 10th bird of that species that she can find in the park. her conclusion is that the birds living in the park who belong to that species generally feed on insects. rachel's sample is . based on the sample she picked, rachel's generalization is