# Statistics for Environmental Engineers

Скачать в pdf «Statistics for Environmental Engineers»

40-49.9

1

0.007

0.986

50-59.9

1

0.007

0.993

60-69.9

0

0.000

0.993

70-79.9

1

0.007

1.000

Source: Prof. David Jenkins, University of California-Berkeley.

15.4 Rankit Regression. The table below gives eight ranked observations of a lognormally distributed variable y, the log-transformed values x, and their rankits.

(a) Make conventional probability plots of the x and y values. (b) Make plots of x and y versus the rankits. (c) Estimate the mean and standard deviation. ND = not detected (<MDL).

y    ND    ND 11.6    19.4    22.9    24.6    26.8    119.4

15.5 Cohen’s Method—Normal. Use Cohen’s method to estimate the mean and standard deviation of the n = 26 observations that have been censored at yc = 7.

15.6 Cohen’s Method—Lognormal. Use Cohen’s method to estimate the mean and standard deviation of the following lognormally distributed data, which has been censored at 10 mg/L.

14    15    16 ND 72 ND 12 ND ND 20    52    16    25    33 ND 62

15.7 PCB in Sludge. Seven of the sixteen measurements of PCB in a biological sludge are below the MDL of 5 mg/kg. Do the data appear better described by a normal or lognormal distribution? Use Cohen’s method to obtain MLE estimates of the population mean and standard deviation.

ND ND ND ND ND ND ND 6    10    12    16    16    17

19    37    41

# 16

## Comparing a Mean with a Standard

KEY WORDS t-test, hypothesis test, confidence interval, dissolved oxygen, standard.

Скачать в pdf «Statistics for Environmental Engineers»