Statistics Spreadsheets, needed today!

Instructions

  Directions: Please answer all questions. There are 15 questions total. The point value for each question is listed below (100 points total). All answers are to be contained in one excel file. Data needed to complete the answers are contained in this excel file. The article needed to complete question #8 is given as an attachment with the spreadsheet.

Question 1

You are given the length of stay (in days) for the following group of patients (cells I & J). A) Calculate the average length of stay (in days). B) What length of stay (in days) occured the most often? C) What is the middle number (in days) for length of stay?

Question 2

Construct a chart for the frequency distribution of ER wait times. "ER Wait Time" values are given on a separate tab within this workbook.

Question 3

You are given the following contingency table: a) Calculate the totals. b) Calculate the joint probabilities and marginal probabilities. c) Make a new contingency table using the probabilities that you just calculated. d) What is the probability that a subject has a systolic BP < 120 mmHg or is a coffee drinker? e) What is the probability that a subject has a systolic BP < 120 mmHg and is a coffee drinker?

Question 4

You are given data titled "Out of INR Range". See the associated Excel tab. This data depicts how often four groups of patients (control patients, patients with bleeding history, patients with clotting history, and patients with combined bleeding and clotting history) are outside of their target INR range. (INR is used to determine warfarin dosing for anticoagultion managment.) From this data perform the following: a) Calculate the mean % outside of target INR range for each of the four groups. b) Construct a bar graph that shows the average % outside of target INR range for each group of patients. Include title, axis titles, etc. Include standard error bars. c) Using 95% CI, calculte and upper and lower confidence limit for the control group.

Question 5

A researcher wants to survey the membership of a state association of school psychologists. The survey will ask if they endorse an increase in annual dues. Names and addresses of each member are maintained on a computer file arranged by zip code and by alphabetical order within zip code. Offer a critique of each of the following methods for drawing a sample of the membership: a. Every 10th name is selected beginning with the first name on the list. b. Within each zip code, the person in the middle of that subsample is chosen. c. Persons who have been members of the association for fewer than two years are sampled.

Question 6

You would like to determine if there is a difference in the mean INR for two groups of patients that have different preferences for drinking cranberry juice. INR (international normalized ratio) is a unit-less “measurement” used to quantify the effectiveness of Warfarin, an anticoagulation drug. The first group consists of 40 patients who like to drink one glass of cranberry juice every morning. The mean INR for the cranberry juice drinkers is 1.5 with sample variance of 1.8. The second group does not drink cranberry juice and consists of 120 subjects. The non-cranberry juice drinking group has a mean INR of 1.1 with sample variance of 0.4. Assume that drinking cranberry juice and not drinking cranberry juice is the only key distinction between the groups (i.e. other dietary factors are held constant and do not effect INR). a) Make the appropriate t-test. b) Determine the probability of the t-test result. c) Decide whether you would accept or reject the hypothesis of no difference between the cranberry juice drinkers and the non-cranberry juice drinkers.

Question 7

You would like to know if there are differences in costs for annual visits between four different primary care practices. Refer to the data under the Excel tab "Primary Care Practices". Use the 0.05 level of significance to: a) Perform a one-way ANOVA to look for differences in costs between primary care practices. b) Look at the F statistic and p value to determine if you should accept or reject the null hypothesis that there is no significant difference between practices.

Question 8

Refer to the following article and answer questions a-g below: Crawford, D. A., Scully, W., McFadden, L., & Manoso, M. (2011). Preoperative Predictors of Length of Hospital Stay and Discharge Disposition Following Primary Total Knee Arthroplasty at a Military Medical Center. Military Medicine, 176(3), 304-307.  a) What was the purpose of this research study? b) Refer to Table 1, Preoperative Risk Factors Relative to LOHS. Which preoperative risk factors are statistically significant? c) Comment on the data distribution in Figure 1. What is the skew of this data? What can you infer from this data skew? d) Refer to Table 3, Odds Ratio of Discharge to a SNF Based on Age and ASA Classification. Comment on what the odds ratios indicate for each of the four age groups. e) Refer to the last sentence on page 304, "Unpaired t tests and analysis of variance were used to compare each variable or groups of varaibles to the dependent outcomes. 1. Name one dependent outcome. 2. Describe a result within the article that would have been determined using analysis of variance. f) Name one limitation of this study. g) Name one predominant strength of this study.

Question 9

Multiple Choice: A confidence interval was used to estimate the proportion of statistics students that are females. A random sample of 72 statistics students generated the following 90% confidence interval: (0.438, 0.642). Based on the interval above, is the population proportion of females equal to 0.60? A) No. The proportion is 54.17%. B) Yes, and we are 90% sure of it. C) Maybe. 0.60 is a believable value of the population proportion based on the information above. D) No, and we are 90% sure of it.

Question 10

You are the VP for the cardiovascular service line at a hospital. A nurse manager on the step-down-unit tells you about a study she just read that she thinks could benefit her floor. According to her, the study says that if the song "Marry had a little lamb" is played when a patient at risk for falls tries to get out of his chair or bed, nurses are more likely to respond to this cue than to the patient call alarm. The reason is the song is found to be irritating and the nurse wants it to stop. The only way the song will stop is if the nurse acknowledges the alarm from the patient's room. She believes that if this idea is implemented, the floor could potentially decrease fall rates and associated costs. What would you want to know about this study to guide your decision making process?

Question 11

Multiple Choice: If a particular batch of data is approximately normally distributed, we would find that approximately A) 4 of every 5 observations would fall between ± 1.28 standard deviations around the mean. B) 2 of every 3 observations would fall between ± 1 standard deviation around the mean. C) 19 of every 20 observations would fall between ± 2 standard deviations around the mean. D) All of the above.

Question 12

Multiple Choice: According to the empirical rule, if the data form a "bell-shaped" normal distribution, ________ percent of the observations will be contained within 3 standard deviations around the arithmetic mean. A) 68.26 B) 95.0 C) 75.00 D) 99.7

Question 13

Multiple Choice: In the construction of confidence intervals, if all other quantities are unchanged, an increase in the sample size will lead to a __________________ interval. A) wider B) biased C) narrower D) less significant

Question 14

You need to order wound care supplies for your clinic for the upcoming month. You have two basic pre-packaged kits to choose from. One kit is used for open wounds, and the other kit is used for closed wounds that still require dressing for protection. Last month your order was placed based on historic needs averaged over the past 3 years, which showed that 30% of patients require open wound kits. However, at the end of the month you ended up having too many open wound kits and too few closed wound kits. After consideration, you realized that as of the past year, fewer patients have open wounds based on the progress that has been made in the early treatment phase. You therefore looked at results since this change had been implemented, and calculated that now only 13% of patients require the open wound kit. You expect to see 70 patients in the next month who require wound kits. 13% of 70 patients is approximately 9 patients that you would expect to require the open wound kits. A) What is the probability that 9 or less of these 70 patients will require the open wound kit? B) What is the probabiity that 9 or more of these 70 patients will require the open wound kit? C) Based on your findings in letter A and C, is it sufficient for next month's order to include 13% open wound kits and 87% closed wound kits? Please explain.

Question 15

The proportion of readmission rates for heart failure within 30 days at your institution is believed to be 25% based upon national data. How large a sample of heart failure patients being followed by your institution would you have to look at to confirm this 25% rate with a measurement error (ME) of 0.05?

ER Wait Times

Out of INR Range

Primary Care Practices