An article in The California Aggie for 30 October 2003 ends with the following statement: "This year, the average [SAT] score for admitted students was 1,242, while the average was 1,181 for enrolled students. UCD’s SAT average is well above the nationwide average of 1020." Earlier in the article, it was stated that there are 4786 first-year students at UC Davis this year. The Web site of The College Board lists the mean composite score as 1019 and reports the standard deviation of the scores as 207.

With this information, how would you evaluate the claim by The California Aggie that "UCD's SAT average is well above the nationwide average"?

The article also hints at but does not directly claim that the SAT scores for first-year students improved this year. Would such a claim be justified?


Infestations of the German cockroach, Blatella germanica, are commonly treated by the pesticide diazinon. In one study the persistence of this pesticide on various types of surfaces was investigated. A 0.5% emulsion of diazinon was applied to glass and plasterboard. After 14 days, 18 cockroaches were placed on each surface, and the number that died within 48 hours was recorded. On the glass, 9 cockroaches died, while on the plasterboard, 13 died. [Based on Elray M. Roper and Charles G. Wright, "German cockroach (Orthoptera: Blatelllidae) mortality on various surfaces following application of diazinon," Journal of Economic Entomology, 78 (1985), pp. 733-737.]

(a) Calculate the mortality rates for the two surfaces.

(b) Find a 95% confidence interval for the difference of the two populations.

(c) The researchers expected the diazinon to persist longer on the plasterboard than glass. State appropriate null and alternate hypotheses for comparing the two surfaces.

(d) Test the null hypothesis and report the P-value. What do you conclude?


GreatSchools.net rates George W. Bush Middle School in Tumwater as "Above average" for their 7th grade WASL test results while Tenino Middle School ranks as "Below average." Below are the data. The percentages indicate the proportion of students who meet or exceed state standards on the WASL tests. The goal is that 100% of students meet or exceed state standards. What do you think?

  Math Reading Writing Listening Students tested
State avg 37% 48% 55% 87%  
GWB 46% 52% 53% 90% 235
Tenino 35% 46% 40% 92% 127

(Note: GreatSchools.net doesn't list the listening scores in their testing summaries.)