# CHEM 2204

Chemical Laboratory Techniques

## Statistics Mode on your SHARP Calculator

Using the built-in functions of your SHARP calculator, determine:

1. Mean or Average, x
2. Standard deviation, sx
3. Relative standard deviation, RSD = (sx /x)· 100

for the following set of data: 95, 80, 80, 75, 75, 75, 50

0. 1. 2. Screen Display Put calculator in statistic mode Input 95 (95 M+) Input 80 two times (80 M+) (M+) Input a number, 75, three times (75 STO 3 M+) Input a number, 50, once (50 M+)
75.71428571 13.3630621 17.6493273 Screen Display To display Mean (RCL 4) To display Standard Deviation (RCL 5) To display Relative Standard Deviation (RCL 5 / RCL 4 * 100)

Therefore, for our data, we can write 75.7 ± 13.4 or 75.7 ± 17.6%

Question: “What should I do if I entered (and stored) a wrong data point on my calculator ? I don’t want to re-enter everything!”
Solution (How to correct after realizing one has stored an incorrect value):
(Courtesy of Vicky Tsui, CENV graduate)

1. Continue entering the rest of the data points
2. After that’s done, scroll up with the “up arrow” on the calculator to find the incorrect data value
• The calculator will scroll through a series of “X=” and the corresponding “N=” entries (i.e. X1=___, N1=___, X2=___, N2=___, etc.)
• The “X=” fields represent the data points entered, while “N=” denotes the frequency of the corresponding data value (X)
(for the purpose of the lab, N would equal 1 (default)…. unless if you want to specify the N number of times that a value is repeated)
3. Once the calculator is displaying the incorrect value, “X= ____” , input the desired correction value and press “M+” to store this number in its place

DONE 😀 (proceed to find the mean, SD, etc.)

To clear data set Start over!