Data Analysis 9-8-2015

Bell Ringer – brain teaser A baseball team had won a game 19-17. No errors. But not a single man crossed the plate. How could this be?

From lab on Friday Accuracy is? How close your measurement is to the true value Precision is? How close several measurements are to one another When you tossed the bean bag, were you able to hit the bullseye every time? How about your partners?

Review on accuracy vs precision High or low accuracy? High or low precision? Low accuracy; low precision High accuracy; high precision Low accuracy; high precision High accuracy

Rounding Numbers Rules: If digit to right of the last SF is < 5, do not round. 2.532 2.53 If digit to right of the last SF is > 5, round up. 2.536 2.54 If digit to right of the last SF is = 5 & followed by a non-zero digit, round up. 2.5351 2.54 If digit to right of the last SF is = 5 but not followed by a non-zero digit, look at the last SF. If it’s an odd digit, round it up. If it’s an even digit, do not round. 2.5350 2.54 but 2.5250 2.52

Practice Round 3.5150114 to: A) five significant figures 3.5150 (Rule 1) B) three significant figures 3.52 (Rule 4) C) one significant figure 4 (Rule 3)

You practice Page 41 # 33 Round all numbers to four sig. fig. A) 84,791 kg 84,790 kg B) 38.5432 g 38.54 g C) 256.75 cm 256.8 cm D) 4.9356 m 4.936 m

Graphing Relationships

Why do you think… Why do you think scientists present their data in graphs? Write your thoughts in your notebook.

Why use graphs? To find relationships in data To see if a pattern exists that may help analyze data.

Circle graphs

Circle graphs Pie chart Divided into wedges Useful for showing parts of a fixed whole Parts usually labeled as percents (%) with the circle as a whole representing 100% Looking at the example, how many people like vanilla ice cream?

Bar graph

Bar graphs To show how a quantity varies with factors like time, location, temperature, etc… Quantity measured is on the y-axis (vertical axis) Independent variable is on the x-axis (horizontal axis) Examples would include how rain rates change over 30 years in a location.

Line graphs

Line graphs What you’ll use most in chemistry The points on a line graph represent the intersection of data for two variables. The x axis independent variable (the variable the scientists deliberately change during an experiment) The y axis dependent variable (the variable that changes according to the independent variable)

Best fit line

Best fit line Because the points are scattered, the line cannot pass through all the data points. The best fit line is drawn so that about as many points fall above the line as fall below the line. If the best fit line is straight, there’s a linear relationship between the variables, and they are directly related Slope :

Finding slope

Direct Proportion Two quantities are directly proportional if dividing one by the other gives a constant value. Density = Mass Volume

Direct Proportion

For a fixed amount of gas, Constant = Pressure x Volume Inverse Proportion Two quantities are inversely proportional if their product is constant. For a fixed amount of gas, Constant = Pressure x Volume

Inverse Proportion graphing y = 1 x   yields a straight line

practice Mercury Wood Iron Lead

What needs to be on a graph http://www.beaconlearningcenter.com/weblessons/alltheparts/default.htm

You make a graph with your partner Make sure you choose a graph that is appropriate to your data Make sure you have the following: Title for your graph Title for all axes Units Proper scale Data points with connected lines if appropriate

What’s on your test Units of measurement Scientific notation Density Temperature Dimensional analysis Accuracy vs precision Percent error Significant Figures Rounding numbers Graphing Review tomorrow Test Thursday