1) An estimate is an approximation of a number based on reasonable assumptions, not a guess. Scientists rely on estimates when exact numbers cannot be obtained. 2) Accuracy refers to how close a measurement is to the true value, while precision refers to how close repeated measurements are to each other. Scientists aim for both accuracy and precision. 3) There are several ways to calculate an average - the mean, median, and mode. The mean is the sum of all values divided by the total number. The median is the middle number. The mode is the most frequently occurring number.

1. CHAPTER 2, SECTiON 2 Mathematics and Science

2. ESTIMATION An estimate is an approximation of a number based on reasonable assumptions. This is NOT the same as guessing!! (Remember we DO NOT GUESS IN SCIENCE!!) Scientists must rely on estimates when they cannot obtain exact numbers.

3. Accuracy and precision Accuracy refers to how close a measurement is to the true or accepted value. Precision refers to how close a group of measurements are to each other. We need to try to be BOTH precise and accurate in science.

4. Averages There are several way to determine an “average” They include: Mean Median Mode

5. MEAN To find the mean or numerical average, add all the numbers and then divide by the total number of items in the list. Example: 110+102+94+110+107+110+109=742 742/7 = 106 So, the average is 106

6. MEDIAN The median is the middle number in a set of data. Example: Place the numbers in order from smallest to largest: 94, 102, 107, 109, 110, 110, 110 If your list has an odd number, then the median is the middle number IF the list has an even number add the two middle numbers and divide by two to find the median

7. Mode The mode is the number that appears most often in a list of numbers. Mode is most useful when a list contains many numbers that are the same Example: 94, 102, 107, 108, 110, 110, 110 The mode is 110