Assignment 1 (due October 9, 2013) You and your friend working in a different lab have been given an unknown water…

Assignment 1 (due October 9, 2013)

 

You and your friend working in a different lab have been given an unknown water sample that contains potassium.  You are both asked to measure the potassium concentration in the solution (10 replicate measurements).  The methods that you and your friend are using are different.  The results that were obtained are listed below.  Determine:

 

(a) the concentration, standard deviation and relative standard deviation for the unknown as measured using the two methods (check for outliers!),

(b) calculate the detection limit (3
s) for each method,

(c) compare the standard deviations and evaluate whether the two averages are significantly different (or not) at the 95% confidence level. 

 

Provide calculations for each step.  If a table (t, F or G) value is not available in the book (for example, if looking for a t-value for a degrees of freedom equal to 27 – hypothetical case), just interpolate the two closest values (25 and 30 in this hypothetical case).

 

    

     RESULTS:

  

 

 

Intensity

 

 

 0.000

 0.000

 0.000

 

 

 

 

 

    

   

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

Standard	Method 1	Method 2
Concentration		Intensity
(mg/L)	(nA)	(mV)
			0.000	0.624	1.955
0.488	2.490
0.522	2.166
0.355	1.500
5.000	9.245	15.644
10.000	17.069	31.220
15.000	26.200	44.266
20.000	33.881	62.394
25.000	43.826	75.611
Replicate
26.544	46.977
25.449	49.120
21.053	50.998
24.353	46.615
23.899	49.326
24.010	46.666
25.554	45.291
23.549	42.995
26.008	43.678
24.404	49.012