To understand the interplay of observations and models you must first be able to distinguish between things that we observe and things that we infer from models. Consider the following statements about the Sun. Classify each statement as an observation or as an inference based on the current, accepted model for the Sun. Observations
the photosphere is made mostly of hydrogen and helium
the photosphere emits mostly visible light.
the corona is hotter than the photosphere.
the sun emits neutrinos.
the sun generates energy by fusing hydrogen into helium in its core.
the core temperature is 10 million k
the convection zone is cooler than the radiation zone.
the composition of the photosphere is the same as that of the gas cloud that gave birth to our solar system.

List three major educational changes over the past 100 years that have positively influenced students. explain why these changes were influential.

Acompany is developing a new high­performance wax for cross country ski racing. in order to justify the price marketingwants, the wax needs to be very fast. specifically, the mean time to finish their standard test course should be less thanseconds for a former olympic champion. to test it, the champion will ski the course 8 times. the champion's times(selected at random) are 59.9 61.9 48.8 52.2 46.6 45.3 50.6 and 41.1 seconds to complete the test course. complete parts a and b below.a) should they market the wax? assume the assumptions and conditions for appropriate hypothesis testing are metfor the sample.assume=0.05. what are the null and alternative hypotheses? choose the correct answer below.b) suppose they decide not to market the wax after the test, but it turns out that the wax really does lower the champion'saverage time to less thanseconds. what kind of error have they made? explain the impact to the company of such anerror.

The following are line items from the horizontal analysis of an income statement:increase/ (decrease) increase/ (decrease) 2017 2016 amount percent fees earned $120,000 $100,000 $20,000 20% wages expense 50,000 40,000 10,000 25 supplies expense 2,000 1,700 300 15 which of the items is stated incorrectly? a. fees earned b. supplies expense c. none of these choices are correct. d. wages expense