A researcher wants to know if infant body weight at 1 year predicts the number of drop-in clinic visits during the following year.

The researcher uses an infant scale and notices some problems during pretesting:

For each of the five problems below, answer the following:

• Are problems due to lack of accuracy, lack of precision or both?
• Are problems due to observer, subject or instrument.
• What might be done to increase accuracy and/ or precision?

Problem 1. During scale calibration at 10 pound weight weighs 10.5 lbs.

Problem 2. The scale gives variable results with a mean of 10.01+/- 1.0 lb.

Problem 3. Some babies get scared and try to climb off the scale and the observer has to hold them on it.

Problem 4. Some babies squirm and the pointer on the scale swings wildly up and down.

Problem 5. Some babies are weighed before a meal, some after, some have wet diapers.