type of household

1998

Upper

Lower

1999

Upper

Lower

Overlap:

median income

90% CI +/-

median income

90% CI +/-

i. The t-statistic is a ratio of the departure of an estimated parameter from its notional value and its standard error. In this case, the estimated coefficient of error is 0.262, and the standard error is 0.038, so the t-statistic is 6.89.

ii. Since the sample size is so large (450), the confidence interval of 95% is 1.96

iii. For the female coefficient of error of 0.262, because the t-statistic is so large, ** could be used, because ? For t-distributions is 2.576 at the 99% interval, well below 6.89.

b)

i. unknown

ii. unknown iii. unknown

iv. Estimates of coefficients from within a regression model are generally not independent of one another, so cov (?j, k,)?0. In such cases, information on the covariance between ?j and ?k must be taken into account when calculating the standard error of the difference or confidence intervals. Covariance is not given, so no estimation of statistical significance can be made.

c)

i. One model deals with verbal SAT scores, another deals with ethnicity, and another deals with gender. They are laid out by model.

ii. Unknown.

iii. Estimates of coefficients from within a regression model are generally not independent of one another, so cov (?j, k,)?0. In such cases, information on the covariance between ?j and ?k must be taken into account when calculating the standard error of the difference or confidence intervals. Covariance is not given, so no formal estimation of statistical significance can...

Hypothesis: a longer season is related to the size of the bird population.
b) We now know the values for "slope" and "Y-intercept." We can use the number of days in the season to find the number of birds surviving the season. Approximately 547,000 birds exist, and 214 are killed every day during hunting season, with a standard of error of 415 birds either way. I would assume that there have 35 past hunting seasons. Approximately 15% percent of the variation in the number of birds can be explained by the length of the hunting season.

7)

Sy/x is a function of Sy, but we're not given Sy. Instead, we're given Sb. The smaller Sb is in relation to Sy/x, the more precise the relationship is, though we have no measure of the strength of the correlation. However, a larger r2 indicates a good positive line. So, for every 50 cent increase in the price of gas, there will be approximately 93 more riders, more or less ~17.

8)

a) Research hypothesis: need determines aid. Null hypothesis: need does not determine aid. r2 isn't a determinative fit. The ratio between sb and sy/x is not high. Therefore, this hypothesis is not supported.

b) A confounding factor is that poverty is determined by federal guidelines, and federal government issues aid based on poverty of residents directly to the residents, with the exception of educational funds. What is the definition of Aid?

9)

a) Yes.

b) Lists hypotheses individually, separated from text. Gives context afterwards in following paragraph.

c) Figure 1: describes information flow

Table 1: presenting numeric values

Table 2:…