Stats Quiz 10 & HW

Table 8-8 Ch8#7

7. Calculate the chi-square from the table. The p-value is < 0.005. Is sports participation significantly different for males and females in this sample? (See the "From the Statistician": Methods calculation.)

18. The incidence proportion=108/200 = 54% 19. 55/100 of the cases of injuries in adolescent men are in adolescents who consume alcohol. 20. RR = [98/138]/[10/62] = 0.71/0.16 = 4.44 Adolescent men who consume alcohol are 4.44 times as likely to have traumatic injury compared to those who do not consume alcohol. Ch13#18-20

A cohort study following a group of 200 randomly selected adolescent males finds the results shown in Table 13-10. 18. Calculate the incidence rate for traumatic injury. 19. What is the attributable risk for the exposed group? Interpret the risk in plain English. 20. Calculate the RR of traumatic injury for adolescent males who consume alcohol. Assuming your RR is significant, interpret this value.

C. Just the meatballs

A health department investigation determines the following after an outbreak:What exposure was a significant risk factor? A. Meatballs and Ice cream B. Meatballs, ice cream and soup C. Just the meatballs D. Just the ice cream

D. There is a statistically significant association between concurrent use of dextromethorphan and SSRIs and serotonin syndrome.

A pilot study examines the concurrent use of dextromethorphan and SSRIs (yes/no) and serotonin syndrome (yes/no). The alpha was 0.10 and the power was 0.80. The p value was 0.03. You know this means: A. Use of dextromethorphan increases the risk of serotonin syndrome. B. There is no association between concurrent use of dextromethorphan and SSRIs and serotonin syndrome C. There is a clinically significant association between concurrent use of dextromethorphan and SSRIs and serotonin syndrome D. There is a statistically significant association between concurrent use of dextromethorphan and SSRIs and serotonin syndrome.

Ch13#21-22

A preschool class visited the zoo. As part of the trip, they had a chance to pet a large lizard and then had lunch. Some students brought lunch from home; others bought lunch at the zoo. That evening four students became ill. 21. What is the attack rate associated with petting the lizard? 22. What is the attack rate associated with bringing lunch from home?

21. attack rate = A/(A+B) = 4/5 or 80% 22. attack rate = A/(A+B) = 2/5 or 40% 23. 2/3, or 66.7% 24. Petting the lizard, because it had the highest attack rate 25. Answers will vary. They may include that the student may have washed his or her hands, or his or her immune system may have been strong enough to destroy any contamination ingested. 26. Answers will vary but may include: the student had a virus with similar symptoms, the student held hands with someone who did pet the lizard, etc. **See next card for the 2x2 breakdown. Ch13#21-26

A preschool class visited the zoo. As part of the trip, they had a chance to pet a large lizard and then had lunch. Some students brought lunch from home; others bought lunch at the zoo. That evening four students became ill. 21. What is the attack rate associated with petting the lizard? 22. What is the attack rate associated with bringing lunch from home? 23. What is the attack rate associated with buying lunch at the zoo? 24. Is petting the lizard, lunch from home, or lunch from the zoo the likely source of the contamination? Explain your answer. 25. If petting the lizard is the source of the contamination, how do you explain student number 7? 26. If there were a student who got sick but did not pet the lizard, does this mean petting the lizard is not the source of contamination? What other explanations could there be?

For the blood type O, the infection proportion is p1 = 312/761 ≈ 0.41, odds is w1 = p1/(1-p1) = 0.41/(1-0.41) = 0.694 So, the odds of being infected is 0.694 for blood type O. For the other blood types, the case occurs at p2 = 370/798 ≈ 0.46, odds is w2 = p2/(1-p2) = 0.46/(1-0.46) = 0.852 So, the odds of being infected is 0.852 for other blood types. OR = w1/w2 = 0.694/0.852 ≈ 0.8 or OR = (312x428)/(370x449) ≈ 0.8 The odds ratio is around 0.8, meaning that the odds of infection decreased by 20% for blood type O group compared to other blood types. 95% CI [.654, .978] means that we are 95% confident that the odds of COVID19 infection for blood type O group is 2.2-34.6% lower than other blood types. This indicates that blood type O might protect against infected by COVID19. The CI excludes 1, meaning the result is significant which is consistent with the hypothesis testing result. P-value=0.036 means there is sufficient evidence at significance level of 0.05 to conclude that odds of COVID19 infection are significantly different between blood type O and others. The odds of infection significantly decrease by 20% for blood type O group. OR is used because the patients were infected by the virus before the researchers know the blood type which is likely a case-control study.

A recent article discussed the association of blood type and COVID-19. Using its partial data as in the following table, compute and interpret the odds of infection and the odds ratio of blood type O vs others. We can also derive the 95% CI [.654, .978] and hypothesis testing (P-value=0.036) of the odds ratio. 1. Interpret the result. 2. Why is OR used instead of RR?

A. More nurses with a baccalaureate degree is estimated to pass the exam but this was not a significant difference.

A study examined the relationship between having a baccalaureate degree and passing a cultural competency exam among a group of 987 randomly selected registered nurses at your hospital. The researchers report that more registered nurses with a baccalaureate degree passed the cultural competency exam (OR 1.54, 95% CI 0.98-1.79). Interpret this information. A. More nurses with a baccalaureate degree is estimated to pass the exam but this was not a significant difference. B. Nurses with a baccalaureate degree were significantly more likely to pass the exam. C. 98% of the nurses passed the exam and the 2% that didn't did not have a baccalaureate degree. D. This is an example of a type II error.

C. Chi-square

A study examines the risk of overdose (yes/no) and the use of hydromorphone (yes/no) in a sample of independent teens. What would be an appropriate test to use? A. McNemars test B. Dependent t-test C. Chi-square D. Independent t-test

D. Unable to determine.

A study examines the use of synthetic opioids and neuropathic pain. The Chi-square value is 2.71. You know this means: A. There is a statistically significant association between the use of synthetic opioids and neuropathic pain. B. There is no association between the use of synthetic opioids and neuropathic pain. C. There is a clinically significant association. D. Unable to determine.

1. Nominal, categorical 2. Nominal, qualitative 3. Nominal, mode, mode = participating in sports for males and for the total sample XING: Mode, the mode for males only is 'sports participation' (frequency of 70), the mode for the total sample is also 'sports participation' (frequency of 120) 4. 200/ 250 = 80% Ch8#1-4

A study is completed to examine the relationship between gender and sports participation. It is conducted by randomly surveying ninth-graders at Smith High School. The collected data is shown. 1. What level of measurement is gender? Is it continuous or categorical? 2. What level of measurement is sports participation? Is it qualitative or quantitative? 3. What measure of central tendency can you determine for sports participation? What is the measure of central tendency for males only? Is the measure of central tendency different for the whole sample? 4. If the whole school has 800 students and the 9th grade has 250 students, what percentage of the 9th grade population did you sample?

5. H0: There is no relationship between gender and sports participation 6. Answers will vary but similar to H1: There is a relationship between gender and sports participation. or H1: There is difference between males and females in the sports participation 7. See Table 8-8, next slide 8. Reject the null hypothesis. 9. Type I 10. Decrease alpha (set a smaller alpha prior to the test) 11. The outcome variable is nominal/ordinal. It is an independent sample, and the cell values are all >5. Ch8#5-11

A study is completed to examine the relationship between gender and sports participation. It is conducted by randomly surveying ninth-graders at Smith High School. The collected data is shown. 5. Write an appropriate null hypothesis for this study. 6. Write two alternative hypotheses that correspond to your null hypothesis. 7. Calculate the chi-square from the table. The p-value is < 0.005. Is sports participation significantly different for males and females in this sample? (See the "From the Statistician": Methods calculation.) 8. What should you conclude about your null hypothesis? 9. What type of error might you be making? 10. If you wanted to make the chance of this type of error smaller, what could you do? 11. Why is the chi-square test appropriate for this study?

A. individuals who eat citrus fruit are significantly more likely to develop cold sores

A study that examines the relationship between eating citrus fruit and getting cold sores finds a relative risk of 1.89 with a p value of 0.047. The results indicate at significance level of 0.05: A. individuals who eat citrus fruit are significantly more likely to develop cold sores B. there is not a significant relationship between eating citrus fruit and developing cold sores C. eating citrus fruit is a significant protective factor for developing cold sores D. if individuals have a cold sore and eat citrus fruit they can get better significantly faster

24. H0: 2D and 3D mammograms have the same cancer detection rates. Ha: 2D and 3D mammograms have different cancer detection rates. 25. Type of mammogram, nominal 26. Cancer detection rates 27. Nominal Ch8#24-27

In a random sample of 100 patients with biopsy-confirmed breast cancer, a study examines cancer detection rates with 50 previously collected, 2D mammograms compared to detection rates in 50 previously collected, three-dimensional (3D) mammograms. The alpha selected for this pilot study is 0.10, and the power is 0.80. 24. Write a null and an alternative hypothesis for this study. 25. What is the independent variable? What level of measurement is it? 26. What is the dependent variable? 27. If cancer detection is measured as yes or no, what level of measurement is this variable?

28. You need the p value to know this answer. P-value is for chi-square value of 2.46 29. Fail to reject the null, p > alpha 30. Reject the null, p<alpha 31. Type II Ch8#28-31

In a random sample of 100 patients with biopsy-confirmed breast cancer, a study examines cancer detection rates with 50 previously collected, 2D mammograms compared to detection rates in 50 previously collected, three-dimensional (3D) mammograms. The alpha selected for this pilot study is 0.10, and the power is 0.80. 28. The pilot study reports a chi-square of 2.46. Is there a significant difference between cancer detection rates with these two screening mechanisms? 29. The study reports 2D mammograms detected 70% of cancers and 3D mammograms detected 90% of cancers with a p = 0.12. What decision should the researcher make about the null hypothesis? 30. In a larger study with the same parameters, 2D mammograms detected 75% of cancers and 3D mammograms detected 91% of cancers with a p = 0.01. What decision should the researcher make about the null hypothesis? 31. Knowing the results of the larger study should make the researcher wonder if the conclusion of the smaller pilot study was what type of error?

32. There is a 98% chance a patient has breast cancer when being screened positive (PPV). 33. No, these would be dependent samples and would require McNemar's test. Chi-square must have independent samples. Ch8#32-33

In a random sample of 100 patients with biopsy-confirmed breast cancer, a study examines cancer detection rates with 50 previously collected, 2D mammograms compared to detection rates in 50 previously collected, three-dimensional (3D) mammograms. The alpha selected for this pilot study is 0.10, and the power is 0.80. 32. Additional studies show the sensitivity of the 3D mammogram is 94% and the PPV is 98%. You have a patient with a positive 3D mammogram, indicating a high risk of cancer. She wants to know what the chances are that she actually has cancer. What can you tell her? 33. Instead the study design involved looking at 100 women who had both a 2D and a 3D mammogram to determine which screen had higher detection rates. Would a chi-square test be appropriate? Why or why not?

C. 94.9%

Several days after a wedding, an outbreak of cyclosporiasis occurred among attendees. Of the 108 guests at the wedding, 76 were ill and met the case definition.50 of the 76 who were ill ate the wedding cake.Three of those who were well ate the wedding cake.What is the attack rate for those who ate the wedding cake? A. 65.8% B. 70.3% C. 94.9% D. 46.3%

1. Maternal age < 40, having a support person present, previous births, and epidural anesthesia 2. Length of labor > 12 hours 3. Interval, quantitative 4. Nominal or dichotomous, qualitative Ch13#1-4

The variables in Table 13-7 have been examined to determine the association with length of labor. 1. What are your "exposure" or independent variables? 2. What is your outcome or dependent variable? 3. Instead you measure your dependent variable rounded to the nearest full hour. What level of measurement is it? Is it quantitative or qualitative? 4. Suppose you originally measured this variable as a yes-or-no response to the question, "Did you feel as though you had a very long labor?" What level of measurement was it? Was it a quantitative or qualitative question?

5. Having a support person present (decreased risk of labor >12 hours), having had previous births (decreased risk of labor > 12 hours), and using epidural anesthesia (increased risk of labor > 12 hours) 6. The significance conclusion of 95% CI is consistent with that of the hypothesis testing at 0.05. If 95% CI of RR includes 1, it means those with and without the exposure are just as likely to develop the disease. 7. No, RR is not significant. 8. Yes, compared to those who did not use anesthesia or used IV/IM anesthesia. 9. Answers will vary. For example, maternal age less than 40 years is not significantly associated with the risk of labor > 12 hours. Ch13#5-9

The variables in Table 13-7 have been examined to determine the association with length of labor. 5. If the study has an alpha of 0.05, which variables are associated with the length of labor? Which are associated with a decreased length of labor? Which are associated with an increased length of labor? 6. Note that when the p-value is significant, the RR confidence intervals do not include the value of one. Why? 7. Did maternal age significantly increase the risk of having a labor greater than 12 hours? 8. Did using epidural anesthesia significantly increase the risk of having a longer labor? Compared to whom? 9. Interpret in plain English the RR for maternal age and length of labor.

A. You fail to reject your null hypothesis

You are examining your data using a chi-square test and produce the following SPSS output. What should you conclude about your null hypothesis at significance level of 0.05? A. You fail to reject your null hypothesis. B. You should reformulate your null hypothesis. C. You should reject your null hypothesis.

B. 44.5

You conduct a case control study and determine that five people with Guinea Worm were exposed to water from river A. One person with the disease had no exposure to water from river A. You also determine that ten people without the disease drank from river A and eighty-nine were healthy and did not drink from river A. Calculate the appropriate Odds ratio. A. 14.3 B. 44.5 C. 15 D. 5

B. You can determine the RR for developing pernicious anemia from this data

You randomly select 120 healthy individuals and randomize them into a group given a daily multivitamin and a group who does not take a daily multivitamin. You follow the sample for ten years and identify all cases of pernicious anemia which develop. Which statement is true? A. Your exposure of interest is retrospective B. You can determine the RR for developing pernicious anemia from this data C. You can only determine the odds ratio for pernicious anemia D. You should NOT determine a relative risk since this is a cross sectional design