Why don't scientist say that they have proven their hypothesis true?

According to the graph, the manufacturing of products in the united states greatly increased from 1800 to 1900. greatly decreased from the onset of the civil war to 1900. slowly decreased in 1800 and again in 1900. slowly increased after 1880.

Which of the following describes classical civilizations? they grew slowly and had a very short lifespan. they were unable to carry out long-distance trade. they made lasting impressions in art and architecture.

What is meant by a symmetrical unimodal distribution? a. a distribution is the frequency at which a certain value of a variable is obtained during a study. a symmetric unimodal distribution is a distribution where there is one value with a larger frequency than any other and the pattern of frequencies on the left and right of this larger frequency are mirror images of each other. b. a distribution is a pattern of frequencies for the various values of a variable collected in a study. a symmetric unimodal distribution is a distribution where there is one value with a larger frequency than any other and the pattern of frequencies on the left and right of this larger frequency are mirror images of each other. c. a distribution is the frequency at which a certain value of a variable is obtained during a study. a symmetric unimodal distribution is a distribution where there is a uniform frequency, meaning the frequency of every value is same, and the pattern of frequencies on the left and right of this larger frequency are mirror images of each other.