Statistics
Statistics — Subject Summary
Statistics By: Dr. Mohamed yahia abuelgasem
Statistics صفحة 1 Statistics 25 pregnant women were sampled during the antenatal period, looking at the number of episodes of urinary incontinence. This sample was from a population of 3500. The number of episodes of incontinence per patient was 30, with a standard deviation of 10. What is the standard error of the mean? 2 4 6 8 10 You wish to investigate the time it takes to perform a caesarean section on women with and without pre-eclampsia. At the end of the study you have two groups of women with the duration of caesarean sections recorded for each. It can't be assumed that these are normally distributed. Which non-parametric statistic test would you use? Chi-squared test Linear regression analysis Mann-Whitney U test Pearson’s R test Student’s t-test A researcher is looking at different types of kettles to find out which type of material is better in terms of achieving a quick boiling temperature. The factors affecting the outcome are: the volume of water, the type of material, the electric resistance and the shape of kettle. Which one of the following will be the independent variable for the researcher's first research question? Time to boil Volume Kettle material Starting temperature Shape of the kettle
Statistics صفحة 2 If TP = true positive and FP = false positive, what is represented by the equation TP / (TP + FP)? Likelihood ratio Negative predictive value Positive predictive value Sensitivity Specificity Diagnostic studies frequently use a receiver operating characteristic curve. What do the two axes of the curve represent? Accuracy versus 1/sensitivity Positive likelihood ratio versus negative likelihood ratio Positive predictive value versus negative predictive value Sensitivity versus 1/specificity Sensitivity versus positive predictive value If the mean booking weight of an antenatal population of 125 women was 80 kg and the standard error of the mean was 5 kilograms, what is the 95% confidence interval? 40-120 kg 60-100 kg 65-95 kg 70-90 kg 75-85 kg What are the three leading three causes of maternal death in the UK from the 2003-2005 Confidential Enquiry into Maternal and Child Health (CEMACH) report? Infection, pre-eclampsia and ectopic pregnancy Pre-eclampsia, haemorrhage and infection Thrombosis, haemorrhage and fatty liver Thrombosis, pre eclampsia and amniotic fluid embolism Thrombosis, pre-eclampsia and infection
Statistics صفحة 3 In appraising a study, it is important to assess the suitability of the research, design and methods used in the context of a clinical condition. Which study will provide the best evidence for a diagnostic test? Randomised controlled trial Cross-sectional study Cohort study Case reports Cost-benefit study Using the data in the table below, what is the likelihood ratio for an ultrasound Doppler test for deep vein thrombosis (DVT)? Number of DVT cases Number of non-DVT cases Positive 90 (a) 5 (b) Negative 10 (c) 95 (d) 0.9 10 13.5 18 20 In a proposed clinical trial of a new uterine relaxant drug, what would be associated with an increase in the sample size? A decrease in the type II error rate A decrease in the standard deviation of blood pressure measurements An increase in the difference in the outcomes to be detected An increase in the significant level from 1–5% A decrease in the specified power of study Which statistical test requires a normal population distribution? Chi-squared test Mann-Whitney U test Spearman’s rank correlation Variance estimation test Wilcoxon rank-sum test
Statistics صفحة 4 Which of the following is a quality of the median of a data set? A. It cannot be distorted by skewed data B. It is always higher than the mean C. It is obtained by dividing the sum of the data set by the number of values in the data set D. It is the middle value in a ranked set of data E. It is the most frequently occurring value in a data set What is the World Health Organisation’s definition of the perinatal mortality rate? A. The number of deaths in the 1st week of life per 1,000 live births B. The number of stillbirths and deaths in the first week of life per 1,000 live births C. The number of stillbirths and deaths in the first week of life per 10,000 live births D. The number of stillbirths and deaths in the first week of life per 100,000 live births E. The number of stillbirths and deaths in the first 28 days of life per 1,000 deliveries The Eighth Confidential Enquiry into Maternal Deaths in the United Kingdom defines maternal mortality as: A. The number of deaths per 1000 pregnancies B. The number of deaths per 100,000 pregnancies C. The number of direct and indirect deaths per 100,000 mortalities D. The number of direct and indirect deaths per 10,000 mortalities E. The number of direct and indirect deaths per 100,000 pregnancies Within what time frame does the Centre for Maternal and Child Enquiries (CMACE) consider maternal death to have occurred? A. During pregnancy B. During pregnancy or within 28 days of the end of the pregnancy C. During pregnancy or within 42 days of the end of the pregnancy D. Within 14 days of the end of the pregnancy E. Within 42 days of the end of the pregnancy
Statistics صفحة 5 An early pregnancy unit undertakes a study to look at the average serum βhuman chorionic gonadotrophin (β-hCG) level of women presenting to their unit with vaginal spotting over a 2-month period. The data collected has a normal distribution. The following values are obtained: • Mean = 500 IU/L • N = 200 • Variance = 16 What is the data set’s standard deviation? A. 2 B. 3 C. 4 D. 9 E. 12 An antenatal clinic undertakes a month long study looking at the diastolic blood pressure of women at their antenatal booking visit. The data collected has a normal Gaussian distribution. The following values are obtained: N = 93 Mean diastolic blood pressure = 82 mmHg Variance = 9 What is the standard deviation of the data set? A. 2 B. 3 C. 5 D. 12 E. 18 Which of the following is an aim of clinical audit? A. To reject or accept a null hypothesis B. To assess the extent to which current practice meets a defined set of standards C. To assess differences between two different populations D. To establish what is best practice E. To extrapolate theory into practice
Statistics صفحة 6 A study was designed to look at the relative risk of women with gestational diabetes mellitus (GDM) who delivered babies with a birth weight of over 4.5 kg. The study looked at all births in the Grace Maternity Unit over a period of 1 year and classified whether the woman had GDM or not, and whether their baby weighed more or less than 4.5 kg. Birth weight Diabetic (n) Control (n) Total
4.5 kg 80 50 130 < 4.5 kg 120 950 1070 Total 200 1000 1200 What is the relative risk of women with GDM delivering a baby weighing > 4.5 kg in this study? A. 0.05 B. 0.1 C. 0.4 D. 8 E. 150