 An estimate is an approximation of a number based on reasonable assumptions.  Not the same as guessing!!!  Based on known info  Scientist must sometimes rely on estimates when they cannot obtain exact numbers

 Accuracy – refers to how close a measurement is to the true value.  Precision – refers to how close a group of measurements are to each other.

Neither Accurate or Precise Accurate and Precise Precise but not Accurate

 The significant figures in a measurement include all the digits that have been measured exactly, plus one whose value has been estimated.

Several ways to determine the average number. 1. Mean - is the numerical average by adding up all the numbers and then dividing by the total number of items in the list. 7 Test scores:Mean =

Several ways to determine the average number. 2. Median – the middle number in a set of data. - Place all the numbers in order from smallest to largest. Circle the middle number Median =

Several ways to determine the average number. 2. Mode – the number that appears most often in a list of numbers. - Place all the numbers in order from smallest to largest Mode =

Percent error is used to determine how accurate, or close to the true value an experimental value really is.

 A graph is a useful tool that may help scientist interpret data by revealing unexpected patterns.  Line graph – shows how the responding or dependent variable changes in response to the manipulated or independent variable.  The horizontal axis – runs left to right.  The vertical axis – runs up and down.  Includes a line of best fit – this shows the overall trend of data.  If a graph shows no identifiable trend then there is no relationship between the variables 11

A line of best fit emphasizes the overall trend shown by all the data taken as a whole.

Trend Lines Line ar Trends – A line graph in which the points fall on a straight line Nonline ar Trends – Points don’t fall on the line No Trend – Points are scattered

A B C Safety in the Science Lab

Good preparation helps you stay safe when doing science activities in the lab. Just as in the lab, good preparation helps you stay safe when doing science activities in the field When an accident occurs, no matter how minor, notify your teacher immediately. Then, listen to your teacher’s directions and carry them out quickly.