Assignment #9 STAT 110 May 2010 (32 Pts.)

Assignment #9 – STAT 110 May 2010 (32 pts.)

1 – Comparisons of the Mean Infant Birth Weight for Different Populations of Mothers Data File: NCBirth STAT 110.JMP

In this problem you will use comparative methods to compare the actual mean birth weights of different populations of mothers. The results of your comparisons will be contained in the table below. For each situation be sure to check assumptions and briefly summarize your findings in that regard.

Use appropriate statistical methods to make comparisons of mean birth weight (in ounces or grams, your choice) across the two populations defined by the variables below:  Sex of child (M = male, F = female)  Marital status (M = married, U = not married)  White? (White (W) vs. Non-white (NW))  Hispanic? (Hisp vs. non-Hisp)  Smoked? (Y = yes vs. N = no) a) Use both hypothesis tests and confidence intervals to compare the mean birth weights of the infants born to the two populations defined by the factors above. To organize your results enter them into the table below. For the p-value and CI columns you will need to enter the p-value from the appropriate test for comparing the two population means for each factor and the confidence interval for the difference in those population means, thus for each factor you will only have one p-value and confidence interval. Report the sample size, sample mean, and sample standard deviation (SD) for each level of the factor. For sex of child, marital status, minority status, and Hispanic use two-tailed p-values. For smoking status use a one-tailed test that reflects the research hypothesis that smokers will have infants with a lower mean birth weight than non-smokers. (10 pts.)

Sample Sample SD p-value CI for Difference in Size (n) Mean Population Means Factor Sex of Child Male Female Marital Status Married Not Married White? Non-white White Hispanic? Hispanic Non-Hispanic Smoking Status Smoker Non-smoker b) Briefly comment on the assumptions required for the analyses you conducted in completing the table. Are the assumptions satisfied for each factor? (2 pts.) c) Summarize your findings from part (a) in a clearly written paragraph, citing p-values and use confidence intervals to quantify the size of mean differences for any significant factors. (6 pts.)

2. Brain Waves and Sensory Deprivation An experiment was performed to see whether sensory deprivation over an extended period of time has any effect on the alpha-wave patterns produced by the brain. To determine this, 10 subjects, inmates in a Canadian prison, had baseline alpha-wave frequencies measured. Then these same inmates were placed in solitary confinement for a period of seven days. Following the seven days of solitary confinement their alpha-wave frequencies were measured again resulting in the data shown below. You will need to enter the data into JMP.

P. Gendreau et al., “Changes in EEG Alpha Frequency and Evoked Response Latency During Solitary Confinement”, Journal f Abnormal Psychology, 79, 1972.

Subject Nonconfined Confined Alpha-Wave Alpha-Wave 1 10.7 9.6 2 10.7 10.4 3 10.4 9.7 4 10.9 10.3 5 10.5 9.2 6 10.3 9.3 7 9.6 9.9 8 11.1 9.5 9 11.2 9.0 10 10.4 10.9 a) Conduct an appropriate test to determine if alpha-wave activity is decreased following solitary confinement. Summarize your findings. (5 pts.) b) What are the disadvantages to using a sample of 20 inmates and randomly assigning ten to receive solitary confinement and ten to stay in their normal cells for the purposes of comparing the alpha-wave activity under the two conditions? (2 pts.)

3 – Preeclampsia and Gestational Age Is there evidence to suggest that the mean gestational age at delivery for mothers with preeclampsia (high blood pressure & protein in their urine) is lower than that for mothers with a normal pregnancy? Use JMP to analyze these data. You can enter the data in JMP yourself. You will need two columns, one to denote the group and the other to contain the response, in this case gestational age at birth. Be sure to check assumptions and perform your analysis accordingly. Gestational Age (in weeks): Preeclampsia: 38, 32, 42, 30, 38,35, 32, 38, 39, 29, 29, 32 Normal: 40, 41, 38, 40, 40, 39, 39, 41, 41, 40, 40, 40 a) Perform a hypothesis test answer the question of interest. Be sure to check assumptions and use the appropriate test. Summarize your findings. (5 pts.) b) Find a 95% CI for the difference in the population means. Discuss. (2 pts.)