12. Heavy-metal pollution of various ecosystems is a se- rious environmental thr

Question

12. Heavy-metal pollution of various ecosystems is a se- rious environmental threat, in part because of the potential transference of hazardous substances to humans via food. The article "Cadmium, Zinc, and Total Mercury Levels in the Tissues of Several Fish Species from La Plata River Estuary, Argentina" (Environmental Monitoring and Assessment, 1993: 119-130) reported the following summary data on zinc concentration (ug g) in the liver of fish: Species Mugil liza Pogonias cromis 56 9.15 1.27 61 3.08 1.71

Explanation / Answer

x = x bar +- Z*(s/sqrt(n))

Where, x = range for given confidence interval

X bar = sample mean, n = sample size and s = sample standard deviation

a)

n = 56, x bar = 9.15 , s = 1.27

95% confidence interval value for Z = +-1.645

Thus,

Range= 9.15 +- 1.645*(1.27/sqrt(56))

= (8.87 to 9.43)

b)

n = 61, x bar = 3.08 , s = 1.71

95% confidence interval value for Z = +-2.576

Thus,

Range= 3.08 +- 2.576*(1.71/sqrt(61))

= (2.52 to 3.64)

Interval of Part b(3.64-2.52 = 1.12) is wider than interval for part a(9.43-8.87 = 0.56) despite of large sample size because of large value of standard deviation and confidence interval

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.