The tutor explains, with an example, how to construct a confidence interval for the median. Let’s imagine we have the following data for purchases from a coffee shop, arranged least to greatest: 2.05, 2.05, 2.05, 2.05, 2.05, 2.05, 2.55, 2.55, …
Statistics: a confidence interval for the median Read more »
The tutor shows how to get a best-fit line using Excel or LibreOffice Calc. Let’s imagine you want a best fit line of form y=mx + b for the following data: x y 0 3 2 5 6 10 8 …
Spreadsheets: linear regression in four easy steps on Excel or LibreOffice Calc Read more »
The tutor continues about lists on the TI-83 Plus. I began about lists on the TI-83 Plus back in my post from January 24, 2015. Now I want to continue. My favourite way to enter a list is from the …
TI-83 Plus: more about creating and editing lists Read more »
The tutor shows a hypothesis testing example with a p-value. In yesterday’s post I brought up p-values. Today I’ll give an example: A population is believed to have mean μ0=42.5; a sample of 30 is taken with mean x=41.6, standard …
The tutor explains the concept of p-value. A topic in stats is hypothesis testing. The usual premise: the tester believes they know the mean of a population, but aren’t sure. In such a case, a sample is taken from the …
The tutor follows his earlier post with an implication about holiday weight gain. In yesterday’s post I discussed the surprise that perhaps mean holiday weight gain is no more than a pound; furthermore, I estimated its standard deviation at 3.125lbs. …
Statistics: holiday weight gain: estimating percentage who don’t Read more »
The tutor estimates the standard deviation of holiday weight gain. I hoped to lose weight over the holiday season; alas, I gained a pound. Searching the internet for opinions about it, I came upon this surprising article, which suggests that …
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The tutor continues with the part life example, this time offering a two-sided confidence interval. In my previous post I gave the premise of a part whose mean life (μ) is 36 months, with standard deviation (σ) 10 months. I …
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The tutor gives an example of a confidence interval. Example 1: Let’s imagine a part has mean lifetime thirty-six months, with standard deviation ten months. What minimum time will it last, with 95% confidence? Solution: Let’s use μ for mean, …
The tutor offers proof of a formula he recalls from Stats. In my university Stats courses, a formula referred to often was V(X)=E(X^2)-(E(X))^2 in which V(X)=population variance E(X^2)=expected value of X^2 E(X)=expected value of X Here’s how I believe one …