NAME:

MEASUREMENT AND ERROR ANALYSIS (30 PTS)

1. (2 pts.) Beginning Questions: Write the question or questions that the class answered by doing the experiment.  

• (3 pts.) Procedures: Describe the procedure your group used, including the brand of drink and number of samples, and describe the overall procedure the class used to answer the beginning question(s).

• Data and Observations:
  • (5 pts.) Your Data: Report the absorbance values for each aliquot of solution you used and calculate the concentration of food dye for each sample. (Add rows and/or include another table if you have more samples.)

Table 1: Drink 1

                Dilution Factor:  25%                                                         

                Drink Brand: Powerade                   Drink Color: Red

Sample #	Absorbance	Concentration (mole/L)	FINAL Concentration (mole/L)
1
2
3
4
5
6
7
8
9
10
	Average
	Standard Deviation
	Relative Standard Deviation

(3 pts.) Example Calculations.  Show an example calculation for finding the concentration from Beer’s law.

(Remember to multiply your concentration values by the dilution factor for the final concentration value. For example, if the dilution factor is 20%, multiply by 100/20.)

Show example calculation for relative standard deviation.

• (2 pts.) Q-Test: Cross out any values in the table above that fail the Q-test.  You must show an example calculation below, whether or not the data point fails the Q-test.

(5 pts.) Class data:  Use Excel to create a histogram (bar graph of mean values with standard deviation error bars) comparing the mean undiluted concentration values for all drinks tested by the class. Data sets where error bars overlap are not considered significantly different. Data sets where error bars do not overlap are considered significantly different. You will consider these ranges when comparing two average values (see the Claims and Evidence section below).

• (5 pts.) Claims and Evidence: Provide Claims and Evidence for both your data and the class data. To determine whether two values are statistically different, report the range of values as the Mean ± Standard Deviation:  e.g., 2.7 M ± 0.2 M, where 2.7 M is the Mean and 0.2 M is the SD.  This notation indicates that the actual value is between 2.5 M and 2.9 M. If the two ranges overlap (i.e., the lower end of the larger number is less than the upper end of the smaller number), then the two numbers are not statistically different.  If the two ranges do not overlap, then the averages are statistically different.

• (5 pts.) Reflection:  

Summarize the overall findings of the study. Directly support with data.

Provide an overall assessment of the class data in terms of accuracy and precision. – e.g. did different groups agree with each other, where there any outliers, are the standard deviations large or small?  You should make use of the RSD values when comparing the precision of the data.  

Discuss insights that you gained from this laboratory and considerations to keep in mind if you perform absorbance measurements in the future.