Maximizing the likelihood over the truncated support always leads to strictly greater probability on the truncated region than original pdf?

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Suppose ##\mathbf{X}## is a random variable with a finite support ##\Omega## and with some pdf ##f(\cdot; \mathbf{v}_0)## where ##\mathbf{v}_0## is the parameter vector. Define, ##\mathcal{A}:= \{\mathbf{x}:S(\mathbf{x}) \geq \gamma\} \subset \Omega## and ##\tilde{\mathbf{x}}:=S(\tilde{\mathbf{x}}) = \gamma##, ##\mathcal{B}:=\{\mathbf{x} \geq \tilde{\mathbf{x}}\}## where ##S:\mathbf{x} \mapsto \mathbb{R}^n##. Moreover, suppose that,

$$\#(\mathcal{B} \cap \mathcal{A}) > \#(\neg \mathcal{B} \cap \mathcal{A})$$
and
$$!\exists \mathbf{x}^*>\tilde{\mathbf{x}}:=\arg \max_{\mathbf{x}}S(\mathbf{x}).$$

Then, it implies that,

\begin{align}
\max_{\mathbf{v}}\sum_{\mathbf{x} :S(\mathbf{x}) \geq \gamma} f(\mathbf{x};\mathbf{v}) > \sum_{\mathbf{x} :S(\mathbf{x}) \geq \gamma} f(\mathbf{x};\mathbf{v}_0)
\end{align}

My questions:

1) Is the statement true?;
2) How could I improve the presentation of this proposition?;
3) What are the mildest possible conditions under which (1) will hold?
 
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  • #2
kullbach_liebler said:
2) How could I improve the presentation of this proposition?;
I don't know what a statistical journal would want, but for the purpose of getting an answer on an internet forum, you could give a more verbal statement of the proposition before presenting it using only notation.

\begin{align}
\max_{\mathbf{v}}\sum_{\mathbf{x} :S(\mathbf{x}) \geq \gamma} f(\mathbf{x};\mathbf{v}) > \sum_{\mathbf{x} :S(\mathbf{x}) \geq \gamma} f(\mathbf{x};\mathbf{v}_0)
\end{align}

This appears to say the maximum value of a function ( which is a summation rather than an integration) when taken over a set is greater than the value of that function evaluated at the particular element ##v_o## in that set. Is that the general idea?
 
  • #3
kullbach_liebler said:
1) Is the statement true?
Let ## \mathbf{v_max} ## be a value of ## \mathbf{v} ## which maximizes the sum. What happens when ## \mathbf{v_0} = \mathbf{v_max} ##?
 

1. What is the truncated support in probability distributions?

The truncated support in probability distributions refers to the range of values that are considered possible outcomes for a random variable. It is a subset of the entire range of values for the variable, and any values outside of this subset are considered impossible outcomes.

2. Why is maximizing the likelihood over the truncated support important?

Maximizing the likelihood over the truncated support is important because it allows for a more accurate estimation of the probability of outcomes within the truncated region. This is especially useful in cases where the original probability density function (pdf) may not accurately reflect the true distribution of the data.

3. How does maximizing the likelihood over the truncated support differ from maximizing the likelihood over the entire pdf?

Maximizing the likelihood over the truncated support differs from maximizing the likelihood over the entire pdf in that it only considers the range of values within the truncated region. This can lead to a higher probability for outcomes within the truncated region, as the likelihood is not influenced by unlikely or impossible outcomes outside of this range.

4. Can maximizing the likelihood over the truncated support ever result in a lower probability for outcomes within the truncated region?

No, maximizing the likelihood over the truncated support will always result in a strictly greater probability for outcomes within the truncated region compared to the original pdf. This is because the truncated support only considers a subset of the original range of values, resulting in a more accurate estimation of the probability for outcomes within this range.

5. How can maximizing the likelihood over the truncated support be applied in practical situations?

Maximizing the likelihood over the truncated support can be applied in various practical situations, such as in statistical modeling or data analysis. It can also be used to improve the accuracy of probability estimates in areas such as finance, risk assessment, and decision making.

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