Merge pull request DataScienceSpecialization#1 from bcaffo/master

Update from first pull

06_StatisticalInference/homework/hw1.Rmd

@@ -1,6 +1,6 @@
 ---
 title       : Homework 1 for Stat Inference
-subtitle    : Extra problems for Stat Inference
+subtitle    : (Use arrow keys to navigate)
 author      : Brian Caffo
 job         : Johns Hopkins Bloomberg School of Public Health
 framework   : io2012

06_StatisticalInference/homework/hw1.html

@@ -34,7 +34,7 @@
         <slide class="title-slide segue nobackground">
   <hgroup class="auto-fadein">
     <h1>Homework 1 for Stat Inference</h1>
-    <h2>Extra problems for Stat Inference</h2>
+    <h2>(Use arrow keys to navigate)</h2>
     <p>Brian Caffo<br/>Johns Hopkins Bloomberg School of Public Health</p>
   </hgroup>
   <article></article>  
@@ -169,7 +169,7 @@ <h2>About these slides</h2>
   <article data-timings="">
 
 <div class="quiz quiz-single well ">
-  <p>A random variable takes the value -4 with probabability .2 and 1 with proabability .8. What
+  <p>A random variable takes the value -4 with probability .2 and 1 with probability .8. What
 is the variance of this random variable?</p>
 
 <ol>
@@ -333,7 +333,7 @@ <h2>About these slides</h2>
   <button class="quiz-clear btn btn-danger">Clear</button>
 
   <div class="quiz-hint">
-  <p>The variance is \(E[X^2] - (E[X])^2\)</p>
+  <p>The variance is \(E[X^2] - E[X^2]\)</p>
 
 </div>
 <div class="quiz-explanation">
@@ -447,4 +447,4 @@ <h2>About these slides</h2>
   <script>hljs.initHighlightingOnLoad();</script>
   <!-- DONE LOADING HIGHLIGHTER JS FILES -->
 
-  </html>
+  </html>

06_StatisticalInference/homework/hw1.md

@@ -1,6 +1,6 @@
 ---
 title       : Homework 1 for Stat Inference
-subtitle    : Extra problems for Stat Inference
+subtitle    : (Use arrow keys to navigate)
 author      : Brian Caffo
 job         : Johns Hopkins Bloomberg School of Public Health
 framework   : io2012

06_StatisticalInference/homework/hw2.Rmd

@@ -1,6 +1,6 @@
 ---
 title       : Homework 2 for Stat Inference
-subtitle    : Extra problems for Stat Inference
+subtitle    : (Use the arrow keys to navigate)
 author      : Brian Caffo
 job         : Johns Hopkins Bloomberg School of Public Health
 framework   : io2012

06_StatisticalInference/homework/hw2.html

@@ -34,7 +34,7 @@
         <slide class="title-slide segue nobackground">
   <hgroup class="auto-fadein">
     <h1>Homework 2 for Stat Inference</h1>
-    <h2>Extra problems for Stat Inference</h2>
+    <h2>(Use the arrow keys to navigate)</h2>
     <p>Brian Caffo<br/>Johns Hopkins Bloomberg School of Public Health</p>
   </hgroup>
   <article></article>  

06_StatisticalInference/homework/hw2.md

@@ -1,6 +1,6 @@
 ---
 title       : Homework 2 for Stat Inference
-subtitle    : Extra problems for Stat Inference
+subtitle    : (Use the arrow keys to navigate)
 author      : Brian Caffo
 job         : Johns Hopkins Bloomberg School of Public Health
 framework   : io2012

06_StatisticalInference/homework/hw3.Rmd

@@ -1,6 +1,6 @@
 ---
 title       : Homework 3 for Stat Inference
-subtitle    : Extra problems for Stat Inference
+subtitle    : (Use the arrow keys to navigate)
 author      : Brian Caffo
 job         : Johns Hopkins Bloomberg School of Public Health
 framework   : io2012
@@ -61,7 +61,7 @@ round(t.test(mtcars$mpg)$conf.int)
 <span class="answer">`r round(max(t.test(mtcars$mpg)$conf.int))`</span>
 
 --- &multitext
-Suppose that data of 9 paired differences has a standard error of $1$, what value would the average difference have to be to have the lower endpoint of a 95%
+Suppose that standard deviation of 9 paired differences is $1$, what value would the average difference have to be so that the lower endpoint of a 95%
 students t confidence interval touch zero?
 
 1. Give the number here to two decimal places
@@ -79,7 +79,7 @@ round(qt(.975, df = 8) * 1 / 3, 2)
 
 
 --- &radio
-An independent group Student's T interval is used over
+An independent group Student's T interval is used instead of
 a paired T interval when:
 
 1. The observations are paired between the groups.
@@ -155,7 +155,7 @@ The interval was conducted subtracting 4 - 6 and was entirely above zero.
 --- &multitext
 Suppose that 18 obese subjects were randomized, 9 each, to a new diet pill and a placebo. Subjects' body mass indices (BMIs) were measured at a baseline and again after having received the treatment or placebo for four weeks. The average difference from follow-up to the baseline (followup - baseline) was 3 kg/m2 for the treated group and 1 kg/m2 for the placebo group. The corresponding standard deviations of the differences was 1.5 kg/m2 for the treatment group and 1.8 kg/m2 for the placebo group. The study aims to answer whether the change in BMI over the four week period appear to differ between the treated and placebo groups. 
 
-What is the pooled variance estimate? (to 2 decimal places)
+1. What is the pooled variance estimate? (to 2 decimal places)
 
 
 *** .hint