In "A Day's Wait," what mistaken idea about illness did the boy have? Why?

The boy's mistake about his illness was a result of a lack of information and a lack of knowledge about units. Whenever the boy's temperature was taken, no unit was given after the number. The boy just kept hearing that his temperature was 102. He figured he was going to die because he had learned that 44 was fatal. Ultimately, the misunderstanding is a result of two different measuring units being used. The information the boy has about 44 being too high of a temperature is based on the Celsius scale, and the boy's temperature is repeatedly taken and measured using the Fahrenheit scale. The father immediately grasps his son's concern and gently explains the difference in the two units. The boy is quite relieved to hear that 98 is normal on one scale; therefore, he knows that he has a fever, but it isn't nearly 60 degrees too high.

"You poor Schatz," I said. "Poor old Schatz. It’s like miles and kilometers. You aren’t going to die. That’s a different thermometer. On that thermometer thirty-seven is normal. On this kind it’s ninety-eight."