Question

Conductivity is one of many properties measured to evaluate water quality. The table below (also attached as an Excel file) contains conductivity measurements (µS/cm) of groundwater samples from a single well.

First, prepare a graph of the raw data.

Then set up estimates of the conductivity

• population average (95% CI),
• population standard deviation (95% CI), and
• a future individual measurement (95% PI).

Also develop a 95% tolerance interval estimate of the conductivity that will include 99% of the conductivities.

Finally, prepare a table that presents your estimates in a tabulated form.

Your submission should take the form of a word document that includes the graph, the table of estimates, and your calculations.

Conductivity	Week
1220	1
1130	2
1400	3
1400	4
1625	5
1670	6
2100	7
1070	8
1622	9
1680	10
1900	11
1700	12
1600	13
1580	14
1620	15
1700	16
1840	17
1772	18
1325	19
1150	20
1300	21
1400	22
1360	23
1340	24
1250	25
1360	26
1417	27
1810	28
1700	29
1725	30
1500	31
1725	32
1700	33
2000	34
1900	35
2040	36
970	37
1150	38
1100	39
1010	40
880	41
975	42
1300	43
1050	44
1116	45
1350	46
1350	47
1250	48
1250	49
1300	50
1230	51
1250	52
1130	53
1300	54

Answer 1

First, prepare a graph of the raw data.

	Conductivity
count	54
mean	1,436.89
sample standard deviation	301.24

population average (95% CI),

confidence interval 95.% lower	1,356.54
confidence interval 95.% upper	1,517.23

population standard deviation (95% CI), and

a future individual measurement (95% PI).

Predicted values for: Conductivity
		95% Confidence Interval		95% Prediction Interval
Week	Predicted	lower	upper	lower	upper	Leverage
55	1,237.964	1,082.021	1,393.908	651.805	1,824.123	0.076

Also develop a 95% tolerance interval estimate of the conductivity that will include 99% of the conductivities.

tolerance interval 95.% lower	846.48
tolerance interval 95.% upper	2,027.30
half-width	590.41