Stats 4-17  Previous data indicate that 17% of trolls are bifungal (two mushroom hands). Wilfrax Margarn wants to create 95% a confidence interval for bifungalism within his troll tribe. There are 18,000+ trolls in his tribe. a) How many trolls should he randomly sample in order to have a margin of error of 3% or less? b) Suppose his final confidence interval is (.162,.220). What conclusion can you draw between his tribe and the rest of the trolls?

Calculations/Conclusions  Assumed p =.17, find n.  (.162,.220) is the CI. Since it contains.17, we can say that there is insufficient evidence to suggest that Wilfrax’s tribe has lower incidence of bifungalism.

Sample Size calculations for t-test  The margin of error in a t-test confidence interval is t*∙s/√n. If we are interested in capturing a specific margin of error, how should we determine how big of a sample size to use?

Test of the Mean  H 0 : μ = μ 0  H a : μ > μ 0; μ < μ 0; μ ≠ μ 0  Model: t-test must satisfy randomized, nearly normal and sample < 10% of population.  Mechanics:  Statistics to display: n, s, standard error, t-test stat, x-bar.  Sketch t-distribution for null hypothesis. On the curve, put the test statistic and shade the tail or tails.  Conclusion:  Reject or fail to reject based on P-value  Rewrite conclusion in context of original problem  Express any reservations (data collection, skew)

Group Work  In your groups you will test the data that we collected earlier in the year. The average height for men in America is 5 ft 9½ in. The average height for women is 5 ft 4 in.