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Name __________________________ Date_______________ Please turn in at the end of lab. II. Exercises 1. Opening STATA dataset, checking and describing dataset. Using lowbwt from: http://www.stat.brown.edu/Zwu/PHP2500.aspx Save this file into your temp directory and open in STATA. a. How many observations are in this dataset? (answer 100) b. How many variables are in this dataset? (answer 6) . describe Contains data from G:\My Documents\Brown\Biostatistics\Data\lowbwt.dta obs: 100 vars: 6 size: 5,200 (99.9% of memory free) ----------------------------------------------------------------------------storage display value variable name type format label variable label ----------------------------------------------------------------------------sbp double %9.0f systolic blood pressure sex double %9.0f sex gender tox double %9.0f tox toxemia diagnosis for mother grmhem double %9.0f grmhem germinal matrix hemorrhage gestage double %9.0f gestational age apgar5 double %9.0f apgar score at five minutes ----------------------------------------------------------------------------Sorted by: c. Using the information from describe and from the data browser please identify the type of each variable: sbp: nominal categorical ordinal categorical continuous numeric discrete numeric sex: nominal categorical ordinal categorical continuous numeric discrete numeric tox: nominal categorical ordinal categorical continuous numeric discrete numeric grmhem: nominal categorical ordinal categorical continuous numeric discrete numeric gestage: nominal categorical ordinal categorical continuous numeric discrete numeric apgar5: nominal categorical ordinal categorical continuous numeric discrete numeric d. Generally apgar scores 3 or below are considered critical, scores 4-6 are considered low and scores 7+ are considered normal. Please create a new variable named status with the values 1=critical, 2=low and 3=normal. What type of variable is status? nominal categorical ordinal categorical continuous numeric discrete numeric gen status=1 if apgar5<=3 replace status=2 if apgar5>=4 &apgar5<=6 replace status=3 if apgar5>=7 2. Summarize variables a. What percent of babies are considered “critical” according to the apgar5 score? (answer 14%) b. What percent of babies are considered “normal” according to the apgar5 score? (answer 60%) Page 1 of 2 . tab status status | Freq. Percent Cum. ------------+----------------------------------1 | 14 14.00 14.00 2 | 26 26.00 40.00 3 | 60 60.00 100.00 ------------+----------------------------------Total | 100 100.00 a. What is the mean systolic blood pressure? (47.08) b. What is the median systolic blood pressure? (47) c. What is the 90% centile of systolic blood pressure? (63) d. What is the range for systolic blood pressure? (19 – 87) e. What is the interquartile range (Q3-Q1)? ((52.5 – 40)=12.5) f. What is the variance? (130.03) g. What is the standard deviation? (11.40) h. 25% of observations have a systolic blood pressure below _______. (40) . sum sbp, detail systolic blood pressure ------------------------------------------------------------Percentiles Smallest 1% 21.5 19 5% 28 24 10% 32.5 25 Obs 100 25% 40 26 Sum of Wgt. 100 50% 75% 90% 95% 99% 47 52.5 63 65 81 Largest 66 67 75 87 Mean Std. Dev. 47.08 11.40324 Variance Skewness Kurtosis 130.0339 .3480732 3.858349 i. What is the mean systolic blood pressure for babies with a diagnosis of germinal matrix hemorrhage? (42.2) j. What is the mean systolic blood pressure for babies without a diagnosis of germinal matrix hemorrhage? (47.94) . sort grmhem . by grmhem:sum sbp -----------------------------------------------------------------------------> grmhem = No Variable | Obs Mean Std. Dev. Min Max -------------+-------------------------------------------------------sbp | 85 47.94118 11.33195 24 87 -> grmhem = Yes Variable | Obs Mean Std. Dev. Min Max -------------+-------------------------------------------------------sbp | 15 42.2 10.91002 19 62 Page 2 of 2