Drilling down beneath a lake in Alaska yields chemical evidence of past changes
ID: 3273269 • Letter: D
Question
Drilling down beneath a lake in Alaska yields chemical evidence of past changes in climate. Biological silicon, left by the skeletons of single-celled creatures called diatoms, measures the abundance of life in the lake. A rather complex variable based on the ratio of certain isotopes relative to ocean water gives an indirect measure of moisture, mostly from snow. As we drill down, we look farther into the past. Here are data from 2300 to 12,000 years ago:
(a) Make a scatterplot of silicon (response) against isotope (explanatory).
Ignoring the outlier, describe the direction, form, and strength of the relationship. The researchers say that this and relationships among other variables they measured are evidence for cyclic changes in climate that are linked to changes in the sun's activity.
weak positive association moderate positive association strong positive association weak negative association moderate negative association strong negative association
Isotope(%) Silicon
(mg/g) Isotope
(%) Silicon
(mg/g) Isotope
(%) Silicon
(mg/g) 19.90 95 20.71 154 21.63 226 19.84 108 20.80 265 21.63 233 19.46 116 20.86 267 21.19 186 20.20 141 21.28 296 19.37 337
Explanation / Answer
a]
Scatter plot of Isotopes and Sillicon
Direction is downward biased that is negative relationship between Isotops and Sillicon. Association moderate negative association
b]
From the above plot we observed that (-19.37, 337) is an outlier.
correlation r = -0.34 ( with outlier)
correlation r = -0.78 ( without outlier)
c]
Yes, the outlier also strongly influential for the regression line.
the regression line with the outlier:
The regression equation is Sillicon = - 1370 - 75.40 Isotope
the regression line without the outlier:
The regression equation is, Sillicon = - 489 - 33.60 Isotope
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