handout_3_3 - 3.3 Toward Statistical Inference Statistical...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
3.3 Toward Statistical Inference Statistical inference is using a fact about a sample to estimate the truth about the whole population. A simple random sample (SRS) of size n consists of n individuals from the population chosen in such a way that every set of n individuals has an equal chance to be the sample actually selected. A parameter is a number that describes the population. A parameter is a fixed number, but in practice we do not know its value. A statistic is a number that describes a sample. The value of a statistic is known when we have taken a sample, but it can change from sample to sample. We often use a statistic to estimate an unknown parameter. EX) A researcher takes a nationwide SRS of 2500 adults that asks if they agree with the statement “I like to shop.” Suppose 1650 agreed. p ˆ = (1650/2500) = 0.66 = 66% p ˆ = 0.66 is a statistic (proportion of sample that agrees) p = ? is a parameter (proportion of population (all US adults) that would agree if asked) If the researcher sampled another 2500 adults, he would almost certainly get a different value for p ˆ . Sampling variability means that the value of a statistic varies in repeated random sampling. if the variation when we take repeat samples from the same population is too great, we can’t trust the results of any one sample advantages of random samples •choosing at random eliminates bias •if we take lots of random samples of the same size from the same population, the variation from sample to sample will follow a predictable pattern What would happen if we took many samples? •take a large number of samples from the same population. •calculate the sample proportion p ˆ for each sample.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern