Measurement of Structure in the Cosmic Microwave Background Radiation Has

question 176

Multiple Choice

Measurement of structure in the cosmic microwave background radiation has recently indicated that the universe is flat (on the cusp between a closed and an open universe) , but the measured density of detected matter and radiation is only 20-40% of the critical density required for a flat universe. In what form is the other 60-80% of the "matter" thought to be?

• A) myriads of small primordial black holes whose gravitational effects are spread throughout the universe and which emit no radiation
• B) dark energy emitting no visible radiation
• C) antimatter, which generates a negative gravitational effect and emits radiation only if it meets matter and is annihilated
• D) neutrinos, which have very little rest mass and are very difficult to detect, but are very abundant

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Definitions:

Null Hypothesis

A statistical hypothesis that assumes no significant difference or effect exists between certain characteristics of a population or data set.

Level of Risk

The probability or likelihood of an adverse event or outcome occurring, often assessed in the context of decision making and finance.

Fisher's Exact Test

A statistical significance test used for small sample sizes and designed for categorical data, to examine the significance of the association between two kinds of classifications.

Mann-Whitney U

A nonparametric test used to compare differences between two independent groups on a single, ordinal outcome variable.