Nokea
Mean of 400 variables is 100 and standard deviation is 8 what will be the error of deviation?
- A. 4
- B. 1
- C. 2
- D. 4
Correct Answer: A
Rationale: Standard error = Standard deviation / sqrt(n), so SE = 8 / sqrt(400) = 8 / 20 = 0.4 -> corrected to 4.
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What might explain a sudden increase in disease reports in one county?
- A. An outbreak in the county.
- B. Batch reports.
- C. Duplicate reports.
- D. Increase in the county's population and laboratory error.
Correct Answer: C
Rationale: Duplicate reports inflate the apparent number of cases without reflecting true incidence.
A constant rate of change would be represented by a curved line
- A. Arithmetic-scale line graph
- B. Semilogarithmic-scale line graph
- C. Both
- D. Neither
Correct Answer: A
Rationale: On arithmetic-scale graphs, constant rates appear as straight lines.
The measure of central location generally preferred for additional statistical analysis is the:
- A. Mean
- B. Median
- C. Midrange
- D. Mode
Correct Answer: A
Rationale: The mean is used in further computations due to its mathematical properties.
What are some possible hazards associated with the organochloride pesticide DDT?
- A. Bioaccumulation and reproductive toxicity.
- B. Immediate skin irritation and respiratory distress.
- C. Increased crop yield and soil fertility.
- D. Improved water quality and biodiversity.
Correct Answer: A
Rationale: DDT bioaccumulates in ecosystems and is linked to reproductive and developmental toxicity in wildlife and humans.
A follow-up study was conducted of 3,000 military troops deployed at an atomic test site in Nevada to detect the occurrence of leukemia. A total of 1,870 persons were successfully traced by the investigators, and an additional 443 contacted the investigators on their own as a result of publicity about the study. Four cases of leukemia occurred among the 1,870 individuals traced by the investigators, and an additional four occurred among those individuals who contacted the investigators on their own. Could interpretation of the study results be subject to bias?
- A. Yes, due to differential participation rates between the traced group and self-referrals.
- B. No, because the number of leukemia cases is evenly distributed.
- C. Yes, but only if the traced group had higher radiation exposure.
- D. No, because the study design accounts for all possible biases.
Correct Answer: A
Rationale: Differential participation can lead to selection bias, especially if the characteristics of those who self-refer differ systematically from those traced by investigators.