







A pie chart 
20161205 

vickie pose la question : Determine the central angle needed to form a pie chart for the following housing characteristic data: 63% owner occupied, 27% renter occupied, and 10% vacant Penny Nom lui répond. 





Brokenline graphs and histograms 
20060216 

George pose la question :
1. What is the main difference between a brokenline graph and a histogram? Both represent continuous variables.
2. What is the correct way to read a multiplication array: xaxis first and then yaxis, other way around or it doesn't matter?
Penny Nom lui répond. 





A normal distribution problem 
20060215 

Mary pose la question : In a certain normal distribution, find the mean when the standard deviation is 5 and 5.48% of the area lies to the left of 78. Penny Nom lui répond. 





The median 
20060127 

Wael pose la question : " median"; what does it mean and how do we calculate it? Penny Nom lui répond. 





Coefficient of variation 
20051019 

Jan pose la question : I am currently teaching the coefficient of variation and am wondering if there are some guidelines as to the interpretation of this statistic. I understand that it measures the variation in a variable relative to the mean  but what is the cut off for "too much" variation expressed in this way???
Andrei Volodin and Penny Nom lui répond. 





Linear regression 
20020116 

Murray pose la question : If you have a set of coordinates (x[1],y[1]),(x[2],y[2]),...,(x[n],y[n]),find the value of m and b for which SIGMA[from 1 to m=n]AbsoluteValue(y[m]m*x[m]b) is at its absolute minimum. Harley Weston lui répond. 





Box and Whisker plots 
20011119 

Rod pose la question : In our Prealgebra course, we have been studying Box and Whisker plots. Recently, we learned how to decide whether a data point is an outlier or not. The book (Math Thematics, McDougall Littell) gave a process by which we find the interquartile range, then multiply by 1.5. We add this number to the upper quartile, and any points above this are considered to be outliers. We also subtract the number from the lower quartile for the same effect. My question: where does this 1.5 originate? Is this the standard for locating outliers, or can we choose any number (that seems reasonable, like 2 or 1.8 for example) to multiply with the Interquartile range? If it is a standard, were outliers simply defined via this process, or did statisticians use empirical evidence to suggest that 1.5 is somehow optimal for deciding whether data points are valid or not? Penny Nom lui répond. 





A confidence interval 
20010628 

Murray pose la question : An investigator wants to find out of there are any difference in "skills" between full and part time students. Records show the following:
Student Mean Score Std Dev Number
   
Full time 83 12 45
Part time 70 15 55
Compute a 95% confidence interval for the difference in mean scores. Andrei Volodin lui répond. 





Mode 
20000922 

James Barton pose la question : I have always been told that a mode is the "one" number that appears most in the set of numbers: ex.{1,3,4,6,3,2} the mode is 3. What if you have {1,1,3,4,5,5}is there a mode. I was taught long ago that there is no mode, Not i am having to teach there is two modes. 1 and 5. If this is the case if we have {1,1,2,2,3,3,4,4,5,5} that every number is the mode. True or false. This is being ambigiuous if we say all are the mode. Because no one number is used more than the others. Claue Tardif and Harley Weston lui répond. 





Sample variance 
20000416 

Jonathan Freeman pose la question : I was just reading your article entitled "A Note on Standard Deviation" I'm now teaching a unit on s.d. and my students were wondering why one uses a denominator of n for a population and n1 for a sample. I saw in your article that this is because "[the quantity] tends to underestimate sigma... and other technical reasons." To which my students again asked... "Why?" Could you please elaborate a bit on the "other technical reasons" perhaps in terms a high school senior (or their teacher...) could understand? Harley Weston lui répond. 





Estimating the population mean 
19991113 

John Barekman pose la question : Statitistics: Estimating the population mean when the standard deviation is known: I am not sure which n to use in the formula for the confidence interval equation: x +/ z*(standard deviation/sqrt(n)) If we have data of ten people, and if we have the data of ten sets of ten people each, what is the difference in the n that we use? What is the difference between the standard deviation and the standard error? Are we using the number of sampling means or just the number of samples? Harley Weston lui répond. 





Stem and Leaf Plot 
19990914 

Jeanette Sovick pose la question : My 5th grade son brought home a math paper, the title of which reads, Reading StemandLeaf Plots...can you explain this so I can explain it to him...There is no book, his teacher just sent this practice sheet home for him to complete and I have no clue! Penny Nom lui répond. 

