Question

Please answer each question with a step-by-step solution using a suitable formula. The estimated sample size shall include a 20% dropout. 1. A study wants to compare lung function in infants exposed to maternal smoking and with a family history of asthma. Power is set at 90% and significance level at 5%. A difference of 0.5 standard deviations is considered to be clinically worthwhile. Equal numbers are considered in each group. Calculate the sample size. 2. Suppose that a clinical investigator is interested in estimating how much reduction will be made of a new cholesterol-lowering drug among recent Bangladeshi immigrants with a given degree of precision. Suppose that the standard deviation for the reduction in cholesterol level equals 40 mg/dl. Calculate the minimum sample size needed to estimate the reduction in fasting serum-cholesterol level if the investigator requires that the 99% confidence interval for the reduction in cholesterol level is no wider than 20 mg/dl. 3. A researcher wants to see the association between birth weight and diabetes in adulthood. The researcher will select a case group: diabetic adults and control group: non-diabetic adults. Both groups will be traced back to data regarding childhood weight. If the researcher thinks that the difference in mean weight between the case and control may be around 350 g and the standard deviation is 1.5 kg, then considering an equal number of cases and control and 90% power at 5% significance, the sample size will be? 4. Suppose that the total cholesterol levels for male college students are normally distributed with a mean of 180 mg/dl and a standard deviation of 80 mg/dl. An investigator would like to examine whether the mean total cholesterol level of the physically inactive male college students is higher than 180 mg/dl using a 5% significance level. Calculate the sample size if the power of the study is set at 90% when the true mean of the total cholesterol level is as large as 210 mg/dl. 5. Suppose the same researcher is interested in knowing the average systolic blood pressure (BP) of children of the same city at a 90% confidence interval and precision of 10 mmHg, and the standard deviation based on previously done studies is 30 mmHg. Calculate the sample size. 6. A researcher wants to see the impacts of weight training exercise on cardiovascular mortality, and according to previous studies, the proportion of cardiovascular death in cases may be around 30% and in control it can be around 60%. Hence, the sample size calculation for a 1% significance level and 80% power with an equal number of cases and control will be? 7. A researcher wants to see the effect of a potential anti-hypertensive drug, and he wants to compare the new drug with placebo. He thinks that if this new drug reduces this blood pressure by 10 mmHg as compared to placebo, then it should be considered as clinically significant. Assume the standard deviation found in previously done studies was 35 mmHg. Suppose the researcher selects the level of significance at 5% and the power of the study at 90%. Calculate the sample size.

Please answer each question with a step-by-step solution using a suitable formula. The estimated sample size shall include a 20% dropout.

1. A study wants to compare lung function in infants exposed to maternal smoking and with a family history of asthma. Power is set at 90% and significance level at 5%. A difference of 0.5 standard deviations is considered to be clinically worthwhile. Equal numbers are considered in each group. Calculate the sample size.

2. Suppose that a clinical investigator is interested in estimating how much reduction will be made of a new cholesterol-lowering drug among recent Bangladeshi immigrants with a given degree of precision. Suppose that the standard deviation for the reduction in cholesterol level equals 40 mg/dl. Calculate the minimum sample size needed to estimate the reduction in fasting serum-cholesterol level if the investigator requires that the 99% confidence interval for the reduction in cholesterol level is no wider than 20 mg/dl.

3. A researcher wants to see the association between birth weight and diabetes in adulthood. The researcher will select a case group: diabetic adults and control group: non-diabetic adults. Both groups will be traced back to data regarding childhood weight. If the researcher thinks that the difference in mean weight between the case and control may be around 350 g and the standard deviation is 1.5 kg, then considering an equal number of cases and control and 90% power at 5% significance, the sample size will be?

4. Suppose that the total cholesterol levels for male college students are normally distributed with a mean of 180 mg/dl and a standard deviation of 80 mg/dl. An investigator would like to examine whether the mean total cholesterol level of the physically inactive male college students is higher than 180 mg/dl using a 5% significance level. Calculate the sample size if the power of the study is set at 90% when the true mean of the total cholesterol level is as large as 210 mg/dl.

5. Suppose the same researcher is interested in knowing the average systolic blood pressure (BP) of children of the same city at a 90% confidence interval and precision of 10 mmHg, and the standard deviation based on previously done studies is 30 mmHg. Calculate the sample size.

6. A researcher wants to see the impacts of weight training exercise on cardiovascular mortality, and according to previous studies, the proportion of cardiovascular death in cases may be around 30% and in control it can be around 60%. Hence, the sample size calculation for a 1% significance level and 80% power with an equal number of cases and control will be?

7. A researcher wants to see the effect of a potential anti-hypertensive drug, and he wants to compare the new drug with placebo. He thinks that if this new drug reduces this blood pressure by 10 mmHg as compared to placebo, then it should be considered as clinically significant. Assume the standard deviation found in previously done studies was 35 mmHg. Suppose the researcher selects the level of significance at 5% and the power of the study at 90%. Calculate the sample size.

Added by Nicol-S R.

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