A scientist takes 40 water samples of the Atlantic ocean in various locations and 40 water samples of the Pacific ocean in various locations. Of the Atlantic samples, there is an average salt concentration of 36 parts-per-thousand (ppt) with a standard deviation of 1 ppt. Of the Pacific samples, the average salt concentration was 34 ppt with a standard deviation of 2 ppt. Is there evidence to suggest a difference in saltiness between the two oceans? Use a 10% significance level. 1. We are comparing two groups, and so it's either going to be a proportion or mean. Are we comparing proportions across two samples or means across two samples? 2. What is the sample size of each sample? Let's call these n1 and n2. 3. What was the average ppt of each sample? Let's call these ¤1 and x2.

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A scientist takes 40 water samples of the Atlantic ocean in various locations and 40 water
samples of the Pacific ocean in various locations. Of the Atlantic samples, there is an average
salt concentration of 36 parts-per-thousand (ppt) with a standard deviation of 1 ppt. Of the
Pacific samples, the average salt concentration was 34 ppt with a standard deviation of 2
pt.
Is there evidence to suggest a difference in saltiness between the two oceans? Use a 10%
significance level.
1. We are comparing two groups, and so it's either going to be a proportion or mean. Are
we comparing proportions across two samples or means across two samples?
2. What is the sample size of each sample? Let's call these n1 and n2.
3. What was the average ppt of each sample? Let's call these T1 and x2.
4. What is the standard deviation of each sample? Let's call these s1 and s2.
5. Find the value of the test statistic for two means.
6. Find the critical value associated with a 10% significance level. This is a two-tailed test.
Since this is on the T-table, use the smaller value of nị or n2.
7. Compare the test statistic to the critical value. Should we reject the null hypothesis of
there being no difference?
Transcribed Image Text:A scientist takes 40 water samples of the Atlantic ocean in various locations and 40 water samples of the Pacific ocean in various locations. Of the Atlantic samples, there is an average salt concentration of 36 parts-per-thousand (ppt) with a standard deviation of 1 ppt. Of the Pacific samples, the average salt concentration was 34 ppt with a standard deviation of 2 pt. Is there evidence to suggest a difference in saltiness between the two oceans? Use a 10% significance level. 1. We are comparing two groups, and so it's either going to be a proportion or mean. Are we comparing proportions across two samples or means across two samples? 2. What is the sample size of each sample? Let's call these n1 and n2. 3. What was the average ppt of each sample? Let's call these T1 and x2. 4. What is the standard deviation of each sample? Let's call these s1 and s2. 5. Find the value of the test statistic for two means. 6. Find the critical value associated with a 10% significance level. This is a two-tailed test. Since this is on the T-table, use the smaller value of nị or n2. 7. Compare the test statistic to the critical value. Should we reject the null hypothesis of there being no difference?
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