Question

which is a valid step in the median-fit method?
○ calculating the slope using the left and middle summary points
○ determining the mean of the x-values and the mean of the y-values
○ finding the three y-intercepts of the summary points using the slope
○ using the largest value of the three y-intercepts to write the equation for the line

Explanation:

1. Recall the median - fit method steps:

• The median - fit method involves dividing the data into three groups, finding the median (summary) points for each group (left, middle, right), calculating the slope using two of these summary points (often left and middle or middle and right), then finding the y - intercepts for the lines through each pair of summary points, and finally using the median of the y - intercepts.
• Option 1: Calculating the slope using the left and middle summary points is a valid step.
• Option 2: Determining the mean of x - values and y - values is part of the mean - fit (least - squares) method, not median - fit.
• Option 3: We find three y - intercepts? No, we find y - intercepts for lines through pairs of summary points, but the process is not about "finding the three y - intercepts of the summary points" (the summary points are (x_med,y_med) for each group, and we find y - intercepts for lines between them, not of the summary points themselves).
• Option 4: We use the median of the y - intercepts, not the largest value.

Answer:

A. calculating the slope using the left and middle summary points