Science: let the results have their say

A prediction is not a result

In our fictional ramp study, students predict that a ball will travel farther from a taller ramp. That is their prediction before measuring. The result comes from what they record afterward. Science does not award a prediction extra points just because someone says it in a very confident voice.

Change one planned factor

The comparison changes ramp height. Students use the same ball, floor, release method, and distance-measuring rule. Keeping relevant conditions alike helps them compare the height settings. If they changed the ball and floor too, it would be harder to tell which change mattered.

Look at every trial

For lower ramp A, the recorded travel distances are seventy, seventy-four, and seventy-two centimeters. For taller ramp B, they are seventy-three, seventy-one, and seventy-two. Do not choose only the largest number from the group you hoped would win. Every recorded trial belongs in the comparison.

Calculate one mean carefully

To find the mean for ramp A, add its three distances and divide by three. Seventy plus seventy-four plus seventy-two is two hundred sixteen. Divide by three to get seventy-two centimeters. The mean is one useful summary of these trials, not a replacement for looking at the actual measurements.

Pause: compare the other mean

Pause and calculate the mean for ramp B. Add seventy-three, seventy-one, and seventy-two, then divide by the number of trials. Compare your answer with ramp A's mean of seventy-two centimeters. Do these recorded means support the prediction that B travels farther?

Say what these trials show

Ramp B also has a mean of seventy-two centimeters. These recorded trials do not support a greater mean distance for B. That does not prove ramp height never matters under any conditions. State the limited result, then consider more careful repeated measurements if investigating further.

Equal means can hide differences

Fun fact: two groups can share a mean without sharing the same measurements. Our ramp A and B values are different, yet both average seventy-two. That is why scientists keep the original observations as well as summaries. One number cannot tell every part of a data story.

Let evidence guide the conclusion

Continue to the worksheet. Identify the changed factor, separate the prediction from the recorded results, and calculate using all the stated trials. Choose a conclusion that fits this study without claiming too much. Changing your mind when evidence differs from your prediction is useful learning.