Question
The water crisis in Flint, MI (see https://en.wikipedia.org/wiki/Flint_water_crisis(Links to an external site.) for more detail) hit the national news in 2016. The person who unveiled
The water crisis in Flint, MI (see https://en.wikipedia.org/wiki/Flint_water_crisis(Links to an external site.) for more detail) hit the national news in 2016. The person who unveiled the lead problem was Marc Edwards, a professor of civil engineering at Virginia Tech University (and a recent McArthur Genius Award recipient for his work!).
According to the Environmental Protection Agency (EPA), water lead levels of 15 ppb (parts per billion) or less are considered to be safe. If lead concentrations exceed 15 ppb in more than 10% of customer water taps sampled, then an unsafe water alert will go out to customers.
The data that was used to uncover this problem is in the table below. Only the tests performed on the first draw (first sample taken from a given source) are included.
SampleID | Zip Code | Ward | Pb Bottle 1 (ppb) - First Draw |
1 | 48504 | 6 | 0.344 |
2 | 48507 | 9 | 8.133 |
4 | 48504 | 1 | 1.111 |
5 | 48507 | 8 | 8.007 |
6 | 48505 | 3 | 1.951 |
7 | 48507 | 9 | 7.2 |
8 | 48507 | 9 | 40.63 |
9 | 48503 | 5 | 1.1 |
12 | 48507 | 9 | 10.6 |
13 | 48505 | 3 | 6.2 |
15 | 48507 | 9 | 4.358 |
16 | 48505 | 5 | 24.37 |
17 | 48505 | 2 | 6.609 |
18 | 48503 | 7 | 4.062 |
19 | 48507 | 9 | 2.484 |
20 | 48507 | 9 | 0.438 |
21 | 48503 | 5 | 1.29 |
22 | 48504 | 6 | 0.548 |
23 | 48504 | 2 | 3.131 |
24 | 48504 | 6 | 120 |
25 | 48505 | 1 | 2.911 |
26 | 48505 | 5 | 16.52 |
27 | 48505 | 1 | 1.984 |
28 | 48503 | 7 | 5.367 |
29 | 48504 | 2 | 5.5 |
30 | 48506 | 4 | 0.639 |
31 | 48503 | 7 | 6.087 |
31 | 48503 | 7 | 10.32 |
33 | 48503 | 6 | 66.88 |
34 | 48505 | 1 | 20.41 |
35 | 48504 | 6 | 109.6 |
36 | 48503 | 8 | 5.06 |
37 | 48504 | 2 | 2.774 |
38 | 48505 | 3 | 4.453 |
39 | 48505 | 1 | 0.4 |
40 | 48529 | 9 | 0.974 |
41 | 48505 | 5 | 3.228 |
42 | 48505 | 2 | 12.55 |
43 | 48505 | 3 | 0.501 |
44 | 48504 | 2 | 2.448 |
45 | 48505 | 3 | 5.508 |
46 | 48504 | 6 | 1.293 |
47 | 48505 | 1 | 4.699 |
48 | 48504 | 6 | 6.093 |
49 | 48504 | 2 | 0.8 |
50 | 48503 | 5 | 1.626 |
51 | 48507 | 8 | 2.576 |
52 | 48504 | 1 | 2.362 |
53 | 48503 | 5 | 1.585 |
54 | 48506 | 4 | 3.058 |
55 | 48506 | 4 | 2.423 |
56 | 48503 | 8 | 30.91 |
57 | 48503 | 8 | 4.47 |
58 | 48505 | 1 | 2.172 |
59 | 48505 | 3 | 1.8 |
63 | 48503 | 5 | 0.965 |
65 | 48505 | 1 | 7.636 |
66 | 48506 | 3 | 3.158 |
67 | 48503 | 7 | 105.3 |
68 | 48506 | 3 | 4.476 |
69 | 48504 | 1 | 2.828 |
71 | 48503 | 5 | 2.481 |
72 | 48507 | 5 | 11.52 |
73 | 48507 | 8 | 3.784 |
74 | 48503 | 5 | 1.344 |
75 | 48504 | 6 | 11.93 |
76 | 48507 | 9 | 10.96 |
77 | 48504 | 6 | 3.341 |
78 | 48503 | 5 | 1.229 |
79 | 48503 | 6 | 6.3 |
79 | 48503 | 6 | 5.153 |
80 | 48504 | 6 | 6.054 |
82 | 48504 | 2 | 31.14 |
83 | 48504 | 6 | 102.7 |
84 | 48504 | 2 | 1.38 |
85 | 48505 | 3 | 1.132 |
87 | 48507 | 9 | 3.232 |
88 | 48532 | 8 | 0.507 |
90 | 48506 | 4 | 8.561 |
91 | 48505 | 3 | 9.997 |
92 | 48504 | 1 | 4.152 |
93 | 48504 | 2 | 75.82 |
95 | 48506 | 4 | 138.8 |
96 | 48507 | 9 | 0.8 |
97 | 48504 | 2 | 7.244 |
98 | 48506 | 3 | 1.621 |
99 | 48505 | 1 | 1.032 |
100 | 48504 | 2 | 0.866 |
101 | 48504 | 2 | 2.525 |
102 | 48505 | 5 | 9.408 |
103 | 48505 | 0 | 0.739 |
104 | 48505 | 1 | 0.9 |
105 | 48504 | 2 | 1.403 |
106 | 48503 | 8 | 5.655 |
107 | 48505 | 2 | 31.06 |
108 | 48506 | 4 | 1.469 |
109 | 48505 | 1 | 23.85 |
110 | 48505 | 2 | 9.766 |
111 | 48505 | 1 | 4.69 |
112 | 48505 | 3 | 4.066 |
113 | 48505 | 1 | 0.846 |
114 | 48505 | 1 | 2.054 |
115 | 48506 | 7 | 3.744 |
116 | 48507 | 9 | 12.9 |
117 | 48505 | 1 | 0.543 |
118 | 48503 | 7 | 6.877 |
119 | 48505 | 1 | 0.552 |
121 | 48506 | 3 | 59 |
122 | 48506 | 4 | 0.349 |
123 | 48506 | 4 | 4.764 |
124 | 48506 | 4 | 0.832 |
125 | 48506 | 4 | 1.224 |
126 | 48507 | 9 | 15.9 |
127 | 48506 | 4 | 5.667 |
128 | 48506 | 4 | 3.564 |
129 | 48506 | 4 | 0.475 |
130 | 48507 | 9 | 5.3 |
131 | 48506 | 4 | 1.166 |
132 | 48506 | 4 | 0.684 |
133 | 48503 | 8 | 6.347 |
134 | 48507 | 9 | 10.56 |
135 | 48502 | 5 | 2.273 |
136 | 48505 | 1 | 1.571 |
137 | 48503 | 8 | 5.402 |
138 | 48504 | 6 | 43.19 |
139 | 48503 | 8 | 1.492 |
140 | 48503 | 5 | 66.24 |
141 | 48505 | 1 | 1.799 |
142 | 48503 | 8 | 1.861 |
143 | 48503 | 8 | 2.672 |
144 | 48505 | 1 | 3.741 |
145 | 48506 | 4 | 1.934 |
146 | 48506 | 4 | 27.05 |
147 | 48506 | 4 | 1.174 |
148 | 48507 | 9 | 2.325 |
149 | 48506 | 4 | 1.966 |
150 | 48506 | 4 | 1.959 |
151 | 48506 | 4 | 0.823 |
152 | 48506 | 4 | 11.2 |
153 | 48504 | 2 | 5.668 |
154 | 48506 | 4 | 6.261 |
155 | 48506 | 4 | 4.797 |
156 | 48506 | 4 | 0.64 |
158 | 48507 | 9 | 8.713 |
159 | 48507 | 9 | 2.544 |
161 | 48507 | 9 | 0.41 |
162 | 48503 | 7 | 32.85 |
163 | 48503 | 7 | 12.87 |
164 | 48503 | 8 | 38.02 |
165 | 48507 | 9 | 2.435 |
166 | 48507 | 9 | 2.997 |
167 | 48507 | 9 | 11 |
168 | 48507 | 9 | 6.219 |
169 | 48503 | 8 | 8.8 |
170 | 48504 | 6 | 8.071 |
171 | 48507 | 9 | 3.262 |
172 | 48503 | 8 | 2.267 |
173 | 48505 | 3 | 0.922 |
174 | 48504 | 6 | 27.02 |
176 | 48503 | 8 | 0.906 |
177 | 48507 | 9 | 2.85 |
178 | 48504 | 2 | 1.852 |
179 | 48506 | 4 | 5.35 |
180 | 48503 | 7 | 25.21 |
182 | 48504 | 6 | 15.55 |
183 | 48506 | 4 | 0.793 |
184 | 48506 | 4 | 5.068 |
185 | 48507 | 8 | 26.64 |
186 | 48506 | 4 | 1.867 |
189 | 48506 | 4 | 19.16 |
191 | 48503 | 5 | 28.7 |
192 | 48507 | 9 | 20.22 |
193 | 48507 | 8 | 2.9 |
194 | 48503 | 7 | 18.86 |
195 | 48507 | 9 | 2.816 |
196 | 48506 | 3 | 118.4 |
197 | 48506 | 3 | 27.45 |
198 | 48503 | 7 | 1.2 |
200 | 48506 | 4 | 4.681 |
201 | 48506 | 3 | 11.57 |
202 | 48532 | 8 | 6.557 |
203 | 48505 | 3 | 3.4 |
204 | 48504 | 6 | 0.7 |
205 | 48507 | 8 | 158 |
206 | 48506 | 4 | 0.977 |
207 | 48503 | 8 | 8.471 |
208 | 48507 | 9 | 11.47 |
209 | 48503 | 7 | 5.228 |
210 | 48507 | 9 | 0.956 |
211 | 48504 | 6 | 1.671 |
212 | 48507 | 9 | 1.152 |
213 | 48507 | 9 | 0.5 |
214 | 48503 | 5 | 10.74 |
215 | 48507 | 9 | 3.9 |
216 | 48507 | 9 | 2.149 |
217 | 48506 | 4 | 1.1 |
218 | 48507 | 9 | 7.087 |
219 | 48505 | 1 | 1.329 |
220 | 48507 | 9 | 6.2 |
221 | 48505 | 3 | 0.8 |
222 | 48503 | 8 | 9.3 |
223 | 48504 | 2 | 2.1 |
224 | 48505 | 1 | 4.563 |
225 | 48504 | 2 | 4.808 |
226 | 48504 | 2 | 0.753 |
227 | 48505 | 1 | 1.862 |
228 | 48503 | 7 | 1.183 |
229 | 48503 | 7 | 8.2 |
230 | 48504 | 6 | 3.679 |
231 | 48505 | 1 | 2.37 |
234 | 48504 | 2 | 0.828 |
235 | 48503 | 7 | 0.719 |
236 | 48504 | 1 | 2.822 |
237 | 48504 | 8 | 2.867 |
238 | 48503 | 7 | 2.332 |
240 | 48503 | 8 | 4.401 |
241 | 48504 | 6 | 2.708 |
242 | 48504 | 6 | 34.13 |
243 | 48503 | 7 | 5.218 |
244 | 48503 | 7 | 15.73 |
245 | 48504 | 6 | 3.045 |
246 | 48503 | 7 | 1.1 |
247 | 48503 | 7 | 1.386 |
248 | 48504 | 6 | 0.915 |
249 | 48504 | 6 | 2.145 |
250 | 48507 | 8 | 4.056 |
251 | 48503 | 7 | 1.668 |
252 | 48503 | 7 | 7.575 |
253 | 48507 | 8 | 5.59 |
254 | 48503 | 5 | 0.708 |
255 | 48504 | 6 | 1.701 |
256 | 48504 | 6 | 1.467 |
258 | 48504 | 2 | 2.582 |
259 | 48505 | 2 | 22.08 |
260 | 48507 | 8 | 16.51 |
262 | 48507 | 8 | 56.26 |
263 | 48504 | 6 | 2.433 |
264 | 48503 | 7 | 0.5 |
265 | 48504 | 6 | 29.13 |
266 | 48505 | 1 | 12.3 |
267 | 48504 | 6 | 3.445 |
268 | 48507 | 9 | 16.49 |
269 | 48503 | 7 | 3.365 |
270 | 48503 | 7 | 1.154 |
271 | 48507 | 9 | 13.53 |
272 | 48504 | 6 | 2.229 |
273 | 48503 | 7 | 28.91 |
274 | 48503 | 7 | 6.601 |
275 | 48507 | 9 | 0.948 |
276 | 48505 | 3 | 3.484 |
278 | 48503 | 7 | 1.888 |
279 | 48503 | 7 | 13.95 |
280 | 48504 | 6 | 6.27 |
281 | 48506 | 7 | 19.12 |
282 | 48507 | 9 | 1.633 |
283 | 48503 | 7 | 1.114 |
284 | 48503 | 7 | 3.9 |
285 | 48504 | 1 | 3.521 |
286 | 48507 | 9 | 3.832 |
287 | 48505 | 3 | 3.243 |
289 | 48503 | 7 | 0.99 |
290 | 48507 | 9 | 1.203 |
291 | 48506 | 3 | 2.261 |
292 | 48503 | 4 | 16.99 |
293 | 48503 | 7 | 3.322 |
294 | 48506 | 4 | 14.33 |
295 | 48503 | 7 | 18.11 |
296 | 48503 | 7 | 12.81 |
298 | 48503 | 7 | 1.083 |
299 | 48503 | 7 | 29.59 |
300 | 48505 | 1 | 4.287 |
Your task is to analyze this data to determine whether the water is safe or not, based on the EPA guidelines indicated above. Your submission for this question should be a PDF file which includes:
- A clear statement of your null and alternate hypotheses, with mathematical notation supplemented with a narrative statement if necessary;
- Excel output with appropriate hypothesis test results (please do not include the original data);
- A judgment about the null hypothesis based on your test results; and
- A clear, practical interpretation of these results that you can present to a non-technical audience. Remember, the question you are answering is, "Should an unsafe water alert be issued?" and you are using the EPA guidelines to make this decision based on the results you obtained.
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