Question

which is a correct step when using the median-fit method for modeling data?
use the median value of y-intercepts found.
calculate slope using the right and middle points.
determine three y-intercepts by using each summary point along with the slope.
determine the median of the x-values and the median of the y-values.

Explanation:

To determine the correct step for the median - fit method:

1. Recall the median - fit method steps: First, we divide the data into three groups. Then we find the summary points (medians of x and y in each group). After finding the slope (usually using left and right summary points), we use each summary point and the slope to find three y - intercepts, and then take the median of these y - intercepts.
2. Analyze each option:

• Option 1: We take the median of the y - intercepts, not just use the median value directly in the process of finding the line. So this is not a correct step in the middle of the method.
• Option 2: The slope is usually calculated using the left and right summary points, not the right and middle. So this is incorrect.
• Option 3: After calculating the slope, we determine three y - intercepts by using each summary point (from the three groups) along with the slope. This is a correct step in the median - fit method.
• Option 4: We find the median of x - values and y - values for each of the three groups (to get summary points), not the median of all x - values and all y - values. So this is incorrect.

Answer:

Determine three y - intercepts by using each summary point along with the slope.