L9 Social Science Statistics
By the end of this lesson, you should be able to:
- Conduct a Hypothesis Test for a single mean with σ known:
- State the null hypothesis (Ho)= the claim or status quo
- and alternative hypothesis (Ha)= what we are trying to prove or find evidence for
- Calculate the test-statistic and p-value of the hypothesis test.
- Assess the statistical significance by comparing the p-value to the α-level.
- Check the requirements for the hypothesis test.
- Show the appropriate connections between the numerical and graphical summaries that support this hypothesis test.
- Draw a correct conclusion for the hypothesis test.
- Interpret a Type I and II error.
- ART= rejecting null hypothesis when it is true (A comes before B so Type 1 error)
- BFF= failing to reject Ho when it is false (B comes after A so Type 2 error)
- Since Type 1 and Type 2 errors are on opposite ends of the spectrum, if you decrease the probability of one error, it will increase the probability of the other.
- We choose the significance level based on the seriousness of making either error.
*P value is the evidence, it is the probability of getting your sample result if the hypothesis is true.
*P value is the probability of getting a test statistic (z-score) that is as extreme or more extreme than the one we got, if the null hypothesis is true.
*P value tells us how much evidence we have against Ho and in favor of Ha.
*The smaller the p value, the greater the chance against the null hypothesis.
>How small is too small?.......significance level ( α)= the decision point for the p-value
>( α) is chosen before collecting data. Common significance levels are .01, .05, .10
The level of significance () controls the probability of committing a Type I Error.
REMEMBER:
>If P is low, Ho must go
>If P is high, keep the guy!
*Hypothesis are always written about parameters and never about statistics.
-NEVER say Ho is true. (Just say that you fail to reject)
*Alternative Hypothesis NEVER has the =.
we label the null hypothesis
. The zero in the subscript represents “null,” “baseline,” “default,” “no effect,” etc. Similarly, we label the alternative hypothesis.
Our alternative hypothesis could have been written as:
- (two-sided hypothesis; two-tailed) *Shade left and right sections in aplet.
- (one-sided hypothesis; left-tailed)
- (one-sided hypothesis; right-tailed)
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