Multicollinearity in polynomial regression can reduce the precision of the coefficient estimates and cause them to be highly sensitive to minor changes in the model. This can lead to unstable and unreliable estimates, making it difficult to interpret the model and infer about the relationships between variables.

The Mann-Whitney U test is a non-parametric test, meaning it can be used when data can't be reasonably fit to a normal distribution.

The primary goal of statistics in data science is to provide a foundation for decision making based on data analysis. It is a discipline that provides tools and methods to interpret and understand data, answer specific questions, and visualize data in a meaningful way. This field of study is crucial in areas where constructing decisions are essential, such as business strategies, scientific research, policy making, etc.

The Central Limit Theorem (CLT) applies to the sampling distribution of the mean for a wide range of underlying distributions, provided the sample size is sufficiently large and the underlying distribution has finite variance.

Sampling in statistical analysis is primarily used to estimate population parameters. Since it's often impractical or impossible to gather data from every individual in a population, we use samples to make inferences about the population as a whole.

The null hypothesis of the Spearman's Rank Correlation test is that there is no monotonic relationship between the variables. That is, changes in one variable do not consistently correspond to changes in the other variable.

The strength of correlation between two variables is determined by the correlation coefficient. A value close to +1 or -1 indicates a strong correlation, while a value close to 0 indicates a weak or no correlation.

Qualitative data represents characteristics or attributes. It is often non-numerical and may include qualities such as textures, colors, smells, tastes, appearance, beauty, etc. This data type is commonly used in fields such as sociology, marketing, and psychology.

A dendrogram is a tree-like diagram that is used in hierarchical clustering to represent the hierarchy of clusters. Each join in the dendrogram represents the two clusters merging, and the height of the join is the distance between those clusters.

The median is usually the most reliable measure of central tendency when a data distribution is skewed. Unlike the mean, the median isn't influenced by extreme values. Therefore, in a skewed distribution, the median generally gives a better idea of the typical value than the mean.