Intro to Statistics, Spring, 2007, Dr. Sinn Solutions in Red
Directions: For each situation, decide if (a) the research described requires a confidence interval (t-interval) or a t-test. For the hypothesis tests, decide (b) if this is a 1 or 2 sample(s) test. For the 2 Samples tests, decide (c) whether you would use the Dependent Samples T-Test or the Independent Samples T-Test. Circle all appropriate items for each research scenario.
T 2 D Researchers use a test called the MLA to determine the foreign language skills of non-native speakers. A university offering a Spanish class for high school foreign language teachers administers the MLA to their 19 students in a standard pre-test/post-test format.
CI A sorority is gathering information on apartments near the NGCSU campus. They price 20 2-Bedroom apartments, run 1-Var Stats on their TI-83 calculators and then estimate with a 95% level of confidence using this data.
T 2 D An analyst for a chain of retail stores wishes to see how this Christmas buying season compares to last year. The early December sales figures of 50 stores from 2002 are compared with this year’s sales in the same 50 stores.
T 1 The Survey of
Study Habits and Attitudes (SSHA) is a psychological test that measures the
motivation, attitude toward school, and study habits of students. Scores range from 0 to 200. The mean score for the population of
T 2 I Researchers claim that increasing calcium intake will reduce high blood pressure. They randomly select two groups of Black males. One group makes no dietary changes while the other takes a calcium supplement. Means are then compared.
T 2 I A
sociologist asks high school students to arrange their classes in order from
favorite to least favorite. Her theory
is that more males than females will list mathematics as their favorite
subject. Thirty males and thirty females
participate.
T 1 Researchers
claim that mothers who use Cocaine during pregnancy have higher incidences of
low birth weight babies. They compared
the birth weights of infants born to 134 mothers who tested positive for
Cocaine use during pregnancy to the statewide statistics reported for babies
born to 5,974 mothers who were drug free using the variance reported in the
statewide study.
CI Hotel conglomerates are doing a survey about the employee loyalty of their managers. They found by surveying 114 hotel managers that the average manager had been with same hotel chain for 11.78 years, and that the standard deviation for these managers was 3.9. Estimate the mean with a 99% confidence level.
T 2 I Researchers claim that loaves of bread lose vitamins as they are stored. A sample of 50 loaves of bread are baked and enriched with vitamins. For 20 loaves, the vitamin content is measured right after baking. The other 30 are measured three days later.
CI You have been hired by the NGCSU Voice to study the mean starting salary of liberal arts majors upon graduation with a bachelor’s degree. From reading some career trajectory literature, you find that standard deviation of studies like this one is usually about $8,000. You randomly select a sample of size 48 and construct an interval estimate with a 93.7% level of confidence.
T 1 Researchers studying the impact of an SAT preparation course assert that their course raises test scores. The mean scores of their 81 students are compared with the national statistics.
CI Three business partners who have started SAT prep courses wish to document their success and estimate an interval likely to contain the average improvement of their course’s graduates on the SAT.
T 2 I Researchers claim that piano lessons improve the spatial-temporal reasoning of preschool children. The spatial-temporal reasoning of 34 children who took piano lessons for 6 months was compared with 44 children of the same age who did not.
T 1 Researchers claim that the cost of internet access is decreasing. They conduct a study in which the average monthly internet charges of 42 randomly selected customers are compared with what a nationwide study determined customers were paying two years ago.
CI Tests for potassium levels in the blood are not perfectly precise, and repeated measures of potassium levels in the same person tend to vary with a standard deviation of about σ = 0.2 (according to repeated research studies reported in medical journals). If Julie’s potassium level is measured on three different days, estimate her mean potassium level with a 85% level of confidence.