[R] Setting up hypothesis tests with the infer library?

[Kevin Zembower]

Hi, Rui and Michael, thank you both for replying.

Yeah, I'm not supposed to know about Chi-squared yet. So far, all of
our work with hypothesis tests has involved creating the sample data,
then resampling it to create a null distribution, and finally computing
p-values.

The prop.test() would work. obviously. I'll look into that. I didn't
know about it.

I'm really struck by the changes in statistics teaching methods,
compared to my first exposure to statistics more than 20 years ago. I
can't ever remember doing a simulation then, probably due to the lack
of computing resources. It was all calculations based on the Normal
curve. Now, we haven't even been introduced to any calculations
involving the Normal curve, and won't be for another two chapters. It's
the last chapter we study in this one-semester course. In this course,
it's all been simulations, bootstraps, randomized distributions, etc.

Thank you, again, Rui and Michael, for your help for me.

-Kevin

On Sat, 2025-03-29 at 16:42 +0000, Rui Barradas wrote:
> Às 16:09 de 29/03/2025, Kevin Zembower via R-help escreveu:
> > Hello, all,
> > 
> > We're now starting to cover hypothesis tests in my Stats 101
> > course. As
> > usual in courses using the Lock5 textbook, 3rd ed., the homework
> > answers are calculated using their StatKey application. In addition
> > (and for no extra credit), I'm trying to solve the problems using
> > R. In
> > the case of hypothesis test, in addition to manually setting up
> > randomized null hypothesis distributions and graphing them, I'm
> > using
> > the infer library. I've been really impressed with this library and
> > enjoy solving this type of problem with it.
> > 
> > One of the first steps in solving a hypothesis test with infer is
> > to
> > set up the initial sampling dataset. Often, in Lock5 problems, this
> > is
> > a dataset that can be downloaded with library(Lock5Data). However,
> > other problems are worded like this:
> > 
> > ===========================
> > In 1980 and again in 2010, a Gallup poll asked a random sample of
> > 1000
> > US citizens “Are you in favor of the death penalty for a person
> > convicted of murder?” In 1980, the proportion saying yes was 0.66.
> > In
> > 2010, it was 0.64. Does this data provide evidence that the
> > proportion
> > of US citizens favoring the death penalty was higher in 1980 than
> > it
> > was in 2010? Use p1 for the proportion in 1980 and p2 for the
> > proportion in 2010.
> > ============================
> > 
> > I've been setting up problems like this with code similar to:
> > ===========================
> > df <- data.frame(
> >      survey = c(rep("1980", 1000), rep("2010", 1000)),
> >      DP = c(rep("Y", 0.66*1000), rep("N", 1000 - (0.66*1000)),
> >             rep("Y", 0.64*1000), rep("N", 1000 - (0.64*1000))))
> > 
> > (d_hat <- df %>%
> >       specify(response = DP, explanatory = survey, success = "Y")
> > %>%
> >       calculate(stat = "diff in props", order = c("1980", "2010")))
> > ============================
> > 
> > My question is, is this the way I should be setting up datasets for
> > problems of this type? Is there a more efficient way, that doesn't
> > require the construction of the whole sample dataset?
> > 
> > It seems like I should be able to do something like this:
> > =================
> > (df <- data.frame(group1count = 660, #Or, group1prop = 0.66
> >                   group1samplesize = 1000,
> >                   group2count = 640, #Or, group2prop = 0.64
> >                   group2samplesize = 1000))
> > =================
> > 
> > Am I overlooking a way to set up these sample dataframes for infer?
> > 
> > Thanks for your advice and guidance.
> > 
> > -Kevin
> > 
> > 
> > 
> > ______________________________________________
> > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > https://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> Hello,
> 
> base R is perfectly capable of solving the problem.
> Something like this.
> 
> 
> year <- c(1980, 2010)
> p <- c(0.66, 0.64)
> n <- c(1000, 1000)
> df1 <- data.frame(year, p, n)
> df1$yes <- with(df1, p*n)
> df1$no <- with(df1, n - yes)
> 
> mat <- as.matrix(df1[c("yes", "no")])
> 
> prop.test(mat)
> #>
> #>  2-sample test for equality of proportions with continuity
> correction
> #>
> #> data:  mat
> #> X-squared = 0.79341, df = 1, p-value = 0.3731
> #> alternative hypothesis: two.sided
> #> 95 percent confidence interval:
> #>  -0.02279827  0.06279827
> #> sample estimates:
> #> prop 1 prop 2
> #>   0.66   0.64
> 
> chisq.test(mat)
> #>
> #>  Pearson's Chi-squared test with Yates' continuity correction
> #>
> #> data:  mat
> #> X-squared = 0.79341, df = 1, p-value = 0.3731
> 
> 
> Hope this helps,
> 
> Rui Barradas
> 
>