# Tutor profile: Erika P.

## Questions

### Subject: Basic Chemistry

Are the following examples heterogeneous mixtures or a homogeneous mixtures? 1) cereal in milk 2) oil and water 3) coffee

1) Cereal is a heterogeneous mixture 2) oil and water is a heterogeneous mixture 3) coffee is a homogeneous mixture In general, here is the difference between a heterogeneous mixture and a homogeneous mixture: -A heterogeneous mixture has a mixed composition where the components of the mixture can be seen easily. These mixtures can have larger particle sizes and the components can be separated more easily. -A homogeneous mixture has a uniform composition where the components of the mixture are not visible to the human eye. These mixtures have particle sizes often at the atomic or molecular level and the components cannot be separated easily or at all.

### Subject: Biology

What are the similarities and differences between osmosis and diffusion?

Similarities: -Both are PASSIVE transporters (meaning they do not require the input of energy) in which particles move from areas of higher concentration to lower concentrations. -They both equalize the concentration of a solution. Key Differences: Osmosis: Diffusion: -only water or another solvent is used -any substance is used - occurs only is a liquid medium -occurs in ANY medium (solid, liquid, or gas) -requires semipermeable membrane -doesn't require semipermeable membrane -depends on solute potential -does not depend on solute potential, pressure potential, or water potential An example of osmosis in the body is the dialysis of the kidneys in the excretory system. An example of diffusion is the removal of toxin and waste substances from the body.

### Subject: Statistics

Given the following situation, determine whether the calculated value of chi-square is statistically significant: Chi Square value of 3.72 (df= 1, alpha= 0.05).

In general, a chi square test (X^2) makes inferences about population differences in proportions between two or more independent groups. For this problem, a statistical table of critical chi square values is needed to compare and determine the statistical significance of an X^2 value of 3.72. When using a critical value chi square table with an alpha value of 0.05 and 1 degree of freedom, the critical chi square value is 3.84. General rule for determining a significant chi square value: - If the calculated chi square value is > (greater than) the chi square critical value than it is SIGNIFICANT. - If the calculated chi square value is < (less than) the chi square critical value than it is NOT SIGNIFICANT. For this problem since our calculated chi square value of 3.72 < 3.84 (critical value), then the calculated value of 3.72 is NOT STATISTICALLY SIGNIFICANT.