? about the amount of transactions within a block

[BitLegit.com]

Is there anyway to predict or manipulate the amount of transactions that are included within a block height?

Wanting to set wagers on the outcome of the total amount of transactions.

[bitbaby]

You mean the number of transactions included in a block? No. There is no magical way of knowing that beforehand. Like there is no way of knowing for sure how much time a block will take to be found, similarly you cannot know for certain that how many transactions will a block contain, the longer it may take a block to be found, the larger the number of transactions it would have, though there is a maximum limit but it is based on the size(which is 1mb currently) not count.

[jambola2]

The number of transactions included is decided by the miners. They can choose 0 transactions or as many transactions to fit the block size. They generally choose to maximize the transactions, since it doesn't cost them anything to add more transactions but they get the transaction fee.

This could hypothetically be manipulated by a large mining group, if the bet was substantial enough that they would want to.
Alternatively, one could add many many small transactions with a high transaction fee to fill the block to maximum size or by adding large transactions to prevent the block from becoming bigger.

There's a myriad of ways to affect it, but no way to real predict it. Also, the ways of affecting it are rather costly and likely not worth the cost unless the bet is large.